Methods and devices for monitoring and controlling thin film processing

ABSTRACT

Thin film processing systems and methods are provided having a moving deposition sensor capable of translation and/or rotation in a manner that exposes the sensor to thin film deposition environments in a flux region substantially the same as the deposition environments experienced by one or more moveable substrates during a selected deposition period. In one embodiment, a thin film monitoring and control system is provided wherein one or more moveable substrates and a moveable deposition sensor are moved along substantially coincident trajectories in a flux region of a thin film deposition system for a selected deposition period. Systems and methods of the present invention may include SC-cut quartz crystal microbalance sensors capable of excitation of at least two different resonant modes.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority under 35 U.S.C. 119(e) to U.S.provisional Patent Application 60/640,539 filed Dec. 30, 2004, which ishereby incorporated by reference in its entirety to the extent notinconsistent with the disclosure herein.

BACKGROUND OF THE INVENTION

Thin film deposition methods enable the fabrication of a wide range ofuseful devices and device components. Chemical and physical thin filmdeposition techniques, such as ion beam sputtering, plasma enhancedchemical thin film deposition, electron beam evaporation and thermalevaporation, for example, are particularly useful methods forfabricating complex structures comprising thin films of a variety ofmaterials, including dielectric materials, semiconductors, andconducting materials. Structures have been fabricated using thin filmdeposition methods having selected thicknesses ranging from 10 s ofnanometers to 10 s of centimeters. The applicability of thin filmdeposition techniques to a wide variety of deposition materials,substrates and processing conditions has lead to widespread adoption ofthese techniques in a number of important fields includingsemiconductors, microelectronics, nanotechnology, lithography and thinfilm optical coatings.

In thin film deposition techniques, a substrate to be coated is placedin contact with a precursor having a selected composition, such as gasphase molecules, ions, atoms and clusters thereof. Condensation of theprecursor itself on a receiving surface of the substrate results information of a thin film layer in physical thin film deposition methods,such as ion beam sputtering and evaporative deposition techniques.Alternatively, in chemical thin film deposition methods, a substrate isexposed to a precursor, which reacts and/or decomposes on the receivingsurface resulting in formation of a thin film layer having a desiredchemical composition. Deposition typically occurs under reduced pressureconditions provided by a vacuum chamber for both physical thin filmdeposition and chemical thin film deposition techniques. In many devicefabrication applications, a receiving surface of a substrate issuccessively and independently exposed to different precursors, therebygenerating complex multilayer structures comprising a plurality ofdistinct thin film layers having different chemical compositions andphysical properties.

In thin film deposition systems, the flux of precursors to a substratedepends on a large number of variables. First, the collision rate ofprecursors to the substrate surface is largely determined by theconcentration (or partial pressure) and translational energy ofprecursors in a region proximate to the substrate surface. Second, thefraction of collisions leading to condensation on or reaction with thesurface depends on the composition of the precursors, composition andmorphology of the substrate surface, the electric charge at the surface,ambient pressure and ambient temperature. Finally, the flux of precursorto a substrate also depends on the geometry defining the relativepositions of the receiving surface of the substrate and the thin filmdeposition source. The amount of material deposited onto the substratesurface at a particular point and at a particular time depends on theflux of precursors to a substrate and on the amount of time this pointon the substrate surface is exposed to the deposition flux. For manythin film deposition systems, a number of these variables vary frompoint to point across a receiving surface; therefore, the flux ofprecursors to the substrate surface is often spatially inhomogeneous.

In many cases, the utility of thin film deposition methods for devicefabrication applications is dependent on the capability of thesetechniques to generate thin film layers having uniform physicalthicknesses, chemical compositions and physical properties, such asrefractive index, density, optical thickness and surface roughness. Manythin film deposition sources, such as sputtering sources and evaporationsources, generate a spatially inhomogeneous source distribution profileof precursors. Spatial inhomogeneity of the concentrations of theprecursors in a region proximate to the substrate can lead to nonuniformfluxes of precursors to the receiving surface. This spatial variabilityof the flux of precursors often results in deposition of thin filmcoatings having thicknesses which vary significantly from point to pointacross the receiving surface of a substrate. Such variability in thethickness of deposited thin film layers can impede the performance ofdevices fabricated using thin film deposition methods. For example,spatial variability in the thickness of thin films comprising multilayerthin film optical components, such as optical interference filters andantireflection coatings, may result in devices having opticaltransmission and/or reflection properties that vary as a function ofposition of a beam on an incident surface.

A number of techniques exist to address problems associated withspatially inhomogeneous source distribution profiles of precursorsgenerated by many thin film deposition sources. One useful method forachieving thin films having improved thickness uniformity uses substratepositioning systems, such as planetary systems, that translate and/orrotate a substrate in a flux region during the thin film depositionprocess. In a dual planet planetary system, for example, one or morerotating planets carry substrates and the rotating planets aretranslated in a circular orbit about a central rotational axis duringdeposition. Translation and rotation of a substrate in this systemexposes different areas of its receiving surface to different precursorconcentrations and energies in a given source distribution profile ofprecursors, thereby providing substantially similar average fluxes ofprecursors over a selected deposition time to all areas of a substratesurface. Use of substrate positioning systems, such as planetarysystems, has been demonstrated to generate thin films having enhancedspatial uniformity with respect to the thickness, composition andmorphology of deposited layers.

In addition to the need for good uniformity, the utility of thin filmdeposition fabrication methods in many applications is also criticallydependent on the capability of these techniques to generate thin filmsand multilayer structures having precisely selected thicknesses andchemical compositions. For example, the optical properties of thin filmoptical components, such as optical interference filters andantireflection coatings, strongly depends on the physical thicknesses,refractive indices and compositions of individual layers comprising amultilayer optical device. Fabrication methods for making multilayeroptical devices having stringent optical specifications, therefore,require accurate and sensitive means for evaluating depositionconditions for determining when a desired thickness of a component thinfilm layer is achieved and, thus, deposition of a subsequent thin filmlayer is to be commenced. As a result of these requirements a number oftechniques have been developed over the last several decades to monitorand control physical and chemical properties of deposited thin filmsduring thin film deposition, such as the thicknesses of deposited thinfilm layers and their chemical composition and optical thickness.

The average flux of precursors provided by many thin film depositionsystems, such as those employing sputtering sources and evaporationsources, undergoes significant variations during deposition of a thinfilm. Therefore, fabrication methods for making thin film devices havingstringent device tolerances require accurate means of monitoring theflux of precursor materials to a substrate in real time. In aconventional thin film deposition system, the flux of precursormaterials is usually determined using a fixed position sensor, such as aquartz crystal microbalance sensor or an optical monitor. Quartz crystalmonitoring is an almost universally applicable technique of determiningthe mass of deposited material, which may be used to determine averagelayer thicknesses via calibration. In contrast to crystal monitoring,optical techniques do not provide a direct measurement of physicalproperties (e.g. mass or physical thickness) of the deposited layers.Rather, optical monitoring techniques detect the temporal evolution oflight transmitted, scattered and/or reflected from a substrate surfacehaving deposited layers, which may be related to thin film thickness,refractive index and composition. The temporal evolution of transmitted,scattered and/or reflected light in these systems, however, also dependssignificantly on the structure and optical properties of underlyingmaterials beneath the thin film layer being deposited. For example, insituations where a thin film layer is deposited on top of a pre-existingstructure of uncertain physical dimensions, composition or opticalproperties optical monitoring does not provide useful information in allcases. Even in the case of deposition of a thin film layer on anuncoated, well defined substrate surface, layer thickness errors fromoptical monitoring can oscillate out of control, and opticallyinsensitive layers can lead to layer thickness errors that becomeimportant when an entire structure is complete. Finally, opticalmonitoring is often susceptible to problems associated with substrateheating and etalon effects in a given optical system. Optical monitoringalso fails when appropriate light sources and detection systems are notavailable.

Due to the drawbacks associated with optical monitoring and the nearuniversal applicability of crystal monitoring, crystal monitoringtechniques are preferred for thin film deposition in many devicefabrication applications. Quartz crystal monitoring as currentlypracticed, however, does not provide a direct measurement of the mass ofmaterials actually deposited on a substrate. Rather, this techniqueprovides a measurement of the mass of material deposited on a sensingsurface of the crystal sensor. As a result of this experimentallimitation, conventional crystal monitoring techniques typically employa fixed position crystal monitor at a location proximate to thesubstrate surface undergoing deposition. This configuration is intendedto provide measurements at the sensing surface of the monitor which maybe related to actual deposition conditions at the substrate. Use of afixed position crystal monitor, therefore, typically requires anexperimental determination of the ratio of the deposition rates at thesensing surface of a fixed position quartz monitor and at the receivingsurface of the substrate. This ratio, commonly referred to as theparts-to-monitor ratio, is used to convert real time measurements of themass of material deposited on the crystal to measurements of the mass ofmaterial actually deposited on the substrate.

The source distribution profile of precursors near the substrate surfaceprovided by many thin film deposition sources is also known to undergovariation during deposition of a thin film. These variations may besignificant and typically result from changes in the operatingconditions of the thin film deposition source, such as variations in ionbeam intensity or target erosion in sputtering sources or variations intemperature, pressure or composition of a sample undergoing evaporationin evaporation sources. As the ratio of the deposition rates at thesensing surface of a fixed position quartz monitor and at the receivingsurface of the substrate is sensitive to variations in the sourcedistribution profile of precursors, the parts-to-monitor ratio undermany experimental conditions is subject to drift during deposition of athin film layer or during deposition of subsequent thin film layers.This drift results in layer thickness errors which can significantlydegrade the quality and/or performance of thin film devices and devicecomponents fabricated via thin film deposition methods.

Alternative approaches of using crystal monitoring techniques to improvethe uniformity of thin films fabricated via thin film deposition havebeen developed in recent years. U.S. Pat. No. 4,858,556 provides adescription of a method for generating thin films employing an in situmobile source processing monitor. In the reported technique, the“amplitude and shape” of a physical thin film deposition source ischaracterized “just prior to substrate processing” and this informationis then used to determine “the non-linear motion scenario that isrequired to achieve processing of specified uniformity over a specifiedarea.” Although the methods and devices described in U.S. Pat. No.4,858,556 are alleged to address problems arising in “processing wheresource distribution profiles often vary substantially from run to run,”these techniques remain susceptible to variations in the sourcedistribution profile of precursors occurring during deposition of a thinfilm layer (i.e. variations during a run, as opposed to variations fromrun to run). In addition, these methods require derivation of complexmathematical relationships relating a measured source distributionprofile of precursors to motion scenarios of substrates required toachieve good uniformity. Mobile source processing monitor configurationsdescribed in U.S. Pat. No. 4,858,556 are limited to embodiments using “asliding contact electrical interface 152 (FIG. 7)” which makes complexmonitor trajectories, such as dual rotation trajectories, impracticaland/or unfeasible. Furthermore, systems provided include mobile sensorsconsisting of only a crystal connecting the crystal electronically toexternal circuitry for reading the crystal frequency via the sliding orrotating electrical contacts. It is very difficult to control thestability of the electrical sensing circuitry in this arrangement due toanticipated changes in conductivity, capacitance, resistance andimpedance upon rotation or sliding motion of the electrical contacts.Therefore, this arrangement is expected to be susceptible to substantialerrors in the measured layer thicknesses arising from the sliding orrotating electrical contacts. Moreover, the configurations disclosed inthis reference are not amenable to high-throughput fabricationapplications.

It will be appreciated from the foregoing that there is currently a needin the art for methods and devices for monitoring and controlling thinfilm processing via thin film deposition. Particularly, devices andmethods for monitoring and controlling thin film deposition are neededthat are capable of measuring and accounting for changes in the averagefluxes and source distribution profiles of precursors generated by thinfilm deposition sources that occur during deposition of a thin filmlayer and subsequent thin film layers. In addition, thin film depositionmethods are needed that are capable of generating thin films havingspatially uniform and accurately selected thicknesses, chemicalcompositions and physical properties.

SUMMARY OF THE INVENTION

The present invention provides thin film processing systems forfabricating thin films and devices comprising thin films having accuratethin film layer control with respect to the physical thickness,thickness profile, chemical composition and physical characteristics ofdeposited thin film layers. The present invention comprises thin filmprocessing methods and devices for depositing precursors onto asubstrate that are capable of generating thin film layers and multilayerstructures comprising thin film layers having accurately selectedphysical thicknesses, thickness profiles, chemical compositions andphysical properties. Thin film processing monitoring systems and methodsare provided that provide real time, in situ measurements of the mass,physical thickness, refractive index, optical thickness, surfacemorphology and/or electrical charge characteristics of a thin film layerdeposited onto a sensor undergoing translation and/or rotation that issubstantially coincident with the translation and/or rotation of asubstrate in a flux region of a thin film processing system. The presentinvention also provides thin film layer monitoring and control methodsfor making single layer and multilayer structures comprising thin filmlayers having spatially uniform physical thicknesses or thin film layershaving selected non-uniform thickness profiles with improved accuracyand precision relative to conventional thin film processing systems.Further, methods and systems of the present invention eliminate relianceon characterization of a parts-to-monitor ratio. Methods and systems ofthe present invention employing an onboard sensor with supportingelectrical circuitry and having a wireless transmitter are capable ofproviding measurements of processing characteristics representative ofthin film processing on a substrate surface while moving in a fluxregion of a thin film processing system along virtually any trajectoryincluding complex trajectories substantially coincident with thetrajectories of one or more substrates in a planetary system, such as adual rotation planetary system.

In one aspect, thin film processing systems and methods are providedhaving a moving deposition sensor capable of translation and/or rotationin a manner that exposes the sensor to thin film deposition environmentsin a flux region substantially the same as the deposition environmentsexperienced by one or more moveable substrates during a selecteddeposition period. In one embodiment, systems and methods are providedwherein a deposition sensor is translated and/or rotated in a mannersuch that the net amount and/or physical properties of precursorsdeposited onto a sensing surface per area of the sensing surface aresubstantially the same as the net amount of precursors deposited onto areceiving surface of substrate per receiving surface area that istranslated and/or rotated in the flux region of a thin film depositionsystem. In another embodiment, a system is provided wherein one or moremoveable substrates and a moveable deposition sensor are moved alongsubstantially coincident trajectories in a flux region of a thin filmdeposition system for a selected deposition period. In yet anotherembodiment, systems and methods are provided wherein a deposition sensoris positioned, translated and/or rotated in a flux region in a mannerproviding an average flux of precursors deposited onto a sensing surfacefor a selected deposition period that is substantially equal to theaverage flux of precursors deposited onto a receiving surface of atranslating and/or rotating substrate undergoing thin film processingvia thin film deposition.

In one embodiment of this aspect of the present invention, systems andmethods for fabricating a thin film layer having a spatially uniformphysical thickness are provided having a rotating sensor that is capableof movement along a trajectory in the flux region of a thin filmprocessing system that is substantially coincident with the trajectoryof one or more substrates undergoing rotation and translation duringthin film processing. A device of the present invention for depositingparticles on the receiving surface of a substrate comprises a thin filmdeposition source for generating a flux of particles in a flux region, arotating substrate having a receiving surface, a means for translatingthe rotating substrate in the flux region, a rotating deposition sensorhaving a sensing surface, and a means of translating the sensor in theflux region. Rotation of the substrate is provided by a means forrotating the substrate that rotates the receiving surface about a firstrotational axis, and rotation of the sensor is provided by a means forrotating the sensor that rotates the sensing surface about a secondrotational axis. In this embodiment of the present invention, rotationand translation of the substrate moves the receiving surface along areceiving surface trajectory in the flux region, and rotation andtranslation of the sensor moves the sensing surface along a trajectoryin the flux region that is substantially coincident with the receivingsurface trajectory. Sensors useful in this embodiment of the presentinvention are capable of measuring the mass, optical thickness,temperature, electric charge, composition or morphology of a thin filmlayer deposited on the sensing surface of the sensor or any combinationof these parameters. Optionally, systems and methods of this aspect ofthe invention may further comprise one or more sourcedistribution-modifying elements, such as shadow masks, positioned in theflux region between substrates undergoing processing and a thin filmdeposition source. Source distribution-modifying elements of the presentinvention are capable of selectively adjusting the distribution ofprecursors that are exposed to one or more substrates undergoing thinfilm processing.

Movement of a substrate in a flux region as it undergoes thin filmprocessing exposes different regions of a receiving surface of thesubstrate to different precursor concentrations in a source distributionprofile of precursors generated by a thin film deposition source. In thepresent invention, the combination of rotation of a substrate about afirst rotational axis and translation of the rotating substrate in theflux region is used to generate spatially uniform thin films on areceiving surface of a substrate despite inhomogeniety in the sourcedistribution profile of precursors generated by most thin filmdeposition sources. Particularly, rotation and translation of thesubstrate exposes each point on the receiving surface to substantiallysimilar net deposition conditions, concentrations and translationalenergies of precursors, during a selected deposition time. Over aselected deposition period that is short relative to the time scale offluctuations of the source distribution, this configuration providessubstantially similar average fluxes of precursors to each point of areceiving surface of the substrate, thereby generating a thin film layeron the receiving surface having enhanced uniformity with respect tophysical thickness, mass and composition.

In the present invention, a sensor is also provided in the flux regionof a thin film deposition source, and is rotated about a second rotationaxis and translated in the flux region provided by a thin filmdeposition source such that during a given deposition period a sensingsurface of the sensor is exposed to substantially identical netdeposition conditions as the rotating and translating substrateundergoing thin film processing. Exposure of the sensor to substantiallyidentical net deposition conditions, for example, can involvepositioning the sensor in the same regions of a source distribution ofprecursor as a substrate undergoing processing for the same timeintervals. This configuration provides substantially the same fluxes ofprecursors to the sensing surface and substrate(s) undergoing thin filmprocessing. In one embodiment, this is achieved by providing acombination of rotational and translational motion of the sensor suchthat the sensing surface of the sensor is moved along a trajectory inthe flux region that is substantially coincident with the trajectorythat the substrate makes during deposition of a thin film. An advantageof this feature of the present invention is that the depositionconditions monitored by the sensor can be directly related to the actualdeposition conditions governing thin film formation on the substratewithout the need for characterizing a parts-to-monitor ratio or assuminga constant source distribution of precursors. As a result, thin filmdeposition systems of the present invention are useful for providingreal time measurements of physical and chemical properties of thin filmsdeposited on a substrate surface that are sensitive to changes in thesource distribution profile of precursors that occur during deposition.Therefore, thin film deposition systems and methods of the presentinvention are capable of generating spatially uniform thin films withprecisely selected physical thickness or thin films having a selected,non-uniform thickness profile using thin film deposition source havingsource distributions of precursors that are subject to variation duringdeposition. This feature of the present invention provides a significantimprovement over conventional thin film deposition systems employing afixed position sensor, which are susceptible to significant thicknesserrors due to variations in the source distribution of precursors duringdeposition of a thin film.

In some embodiments of this aspect of the present invention, one or moresource distribution-modifying elements are provided in the flux regionbetween the thin film deposition source and the rotating and/ortranslating substrates undergoing processing (and also rotating and/ortranslating sensor). For example, the present invention includesembodiments having one or more source distribution-modifying elementscomprising shadow masks which are capable of at least partiallypreventing the passage of some of the precursors as it passes through aparticular region with a particular flux gradient and a particularorientation with respect to this gradient. Typically, shadow maskscomprise plates or grids made of materials, such as metals or plastics,that at least partially prevent the transmission of precursors. Theshapes and physical dimensions of shadow masks, such as surface areapresented to the thin film deposition source and thickness, depend onthe source distribution profile of precursors generated by a given thinfilm deposition source. As a result of their characteristic to partiallyor entirely prevent transmission of precursors from a deposition sourceto a substrate undergoing processing, incorporation of a shadow maskinto the systems of the present invention modifies a source distributionprofile of precursors that are exposed to substrates undergoingprocessing. The modified source distribution profile of precursors ischaracterized by processing regions wherein the flux of precursors ispartially or entirely attenuated. Selective manipulation of the sourcedistribution profile of precursors exposed to one or more substratesundergoing processing using source distribution-modifying elements, suchas shadow masks, is particularly useful in the present invention forgenerating thin film structures having spatially uniform physicalthicknesses and selected nonuniform thickness profiles. The presentinvention includes systems and methods, however, wherein sourcedistribution-modifying elements, such as shadow masks, are used tofabricate thin film structures having a selected, non-uniform thicknessprofile on a receiving surface, such as spatially-chirped structures.

Systems and methods of the present invention may employ a single shadowmask or may include a plurality of shadow masks. In systems and methodsuseful for making multilayer structures and devices employing asputtering thin film deposition source, shadow masks having differentphysical dimensions and/or compositions can be provided for each targetmaterial used during fabrication. The present invention also includessystems and methods using one or more dynamic shadow masks capable ofselectively adjusting (or tuning) the source distribution of precursorsexposed to substrates undergoing processing. Some dynamic shadow masks,for example, are capable of selective adjustment of their physicaldimensions, such as surface area presented to a thin film depositionsource, and/or position in a flux region so as to provide a selectedsource distribution of precursors exposed to a substrate.

In some embodiments, use of a shadow mask is beneficial for achievingthin films exhibiting uniform physical thicknesses across an entire areaof a receiving surface of a substrate. Such embodiments may additionallyprovide good uniformity with respect to the physical thicknesses of thinfilms deposited on a plurality of substrates undergoing simultaneousprocessing. In some aspects, incorporation of a shadow mask is usefulfor providing substantially equivalent average fluxes of precursors tothe receiving surfaces of rotating and/or translating substrates (andsensors) having different trajectories in a flux region. For example,use of one or more shadow masks in the present invention provides ameans of establishing substantially equivalent average fluxes ofprecursors for a selected deposition time to rotating and/or translatingsubstrates (and sensors) positioned on one or more sub-planets of a dualrotation planetary system, particularly substrates (and sensors)provided in different radial positions with respect to the rotationalaxis of one or more sub-planets. In the present invention, use of sourcedistribution-modifying elements, such as shadow masks, in combinationwith single and multiple rotation planetary systems, such as single anddual rotation planetary systems, provides an effective high-throughputmeans of simultaneously fabricating equivalent thin film structureshaving accurately selected physical thicknesses on a plurality ofsubstrates.

Motion of substrates and deposition sensors in the flux region may beperiodic in the present invention. In one embodiment, for example, oneor more rotating substrates and the rotating sensor are repeatedly movedthrough substantially the same cyclic trajectory at substantially thesame rate of rotation and/or translation for a plurality of movementcycles each of which comprises a complete, cyclic trajectory. Whilesubstrates and the sensor move along the same trajectory in thisembodiment of the present invention, each rotating and/or translatingcomponent begins motion at a different starting position and, therefore,different translating and/or rotating components never occupy the sameposition at the same time because these components move along the samecyclic trajectory at the same velocity. An advantage of this motionscenario of substrates and sensors of the present invention, is that useof large translational and rotational velocities and relatively lowdeposition rates results in completion of a large number of cyclictrajectories during deposition of a thin film, thereby providingsubstantially the same net paths in the flux region and net depositionconditions for all translating and or rotating components.Alternatively, the present invention also includes embodiments whereinthe motion of substrates and deposition sensors in the flux region isaperiodic. In this embodiment, the time scale over which the averagedflux on the substrate(s) and sensor(s) are effectively the same and areshort compared to the time scales over which physical properties (e.g.flux distribution, distribution of energies, spatial distribution) ofthe source changes.

In the present invention, rotation and translation of substrates anddeposition sensors may be provided by any means known in the art. Inexemplary embodiments, rotation and translation of these components isprovided by a planetary system, such as single planet and multipleplanet rotation systems. For example, a device of the present inventionfurther comprises a dual rotation planetary system, wherein one or moresubstrates and the deposition sensor(s) are affixed to sub-planets ofthe system for translating and rotating these components in the fluxregion of a thin film deposition system. In one embodiment, thesubstrate(s) and the sensor(s) are independently rotated about first andsecond rotational axis (i.e. the rotational axes of subplanets havingthe sensor and substrate), respectively, by affixing these moveablecomponents to different sub-planets of a dual rotating planetary system.Individual sub-planets are affixed to a central planet of the dualrotation planetary system such that rotation of the central planet movesthe rotating substrate and the rotating sensor in substantially the sameorbit about a central rotational axis of the dual rotation planetarysystem. In an embodiment of the present invention, first and secondrotational axes are positioned the same distance from the centralrotational axis, and the receiving surface of the substrate ispositioned a distance from the first rotational axis equal to thedistance that the sensing surface of the sensor is positioned from thesecond rotational axis. The present invention includes embodimentswherein additional substrates are positioned on a single sub-planet andembodiments wherein additional substrates are positioned on additionalsub-planets rotating about additional rotational axis positioned atabout the same distance from the central axis as the first and secondrotational axes. Use of a dual planetary system in the present inventionis particularly useful for fabricating spatially uniform thin filmshaving accurately selected physical thicknesses, chemical compositionsand physical properties. Moreover, embodiments of the present inventionusing a dual rotation planetary system are capable of high throughputthin film processing compatible with commercial scale device fabricationapplications.

Alternatively, the present invention includes embodiments whereinsubstrates and sensor(s) are affixed to the central planet of a singlerotation planetary system. The system is configured such that rotationof the central planet rotates the substrates and sensor(s) about orbitscharacterized by their individual rotational positions with respect tothe central rotational axis of the central planet. Methods and systemsof this aspect of the present invention may further comprise one or moreshadow masks for providing a selected distribution of precursors at thereceiving surfaces of the substrates and sensing surface of the sensor.In one embodiment, sensors are provided at radial positions with respectto the central rotational axis equal to the radial positions ofsubstrates undergoing processing. In another embodiment, sensors mayalso be provided in a manner such that they rotate about a secondrotational axis, such as a rotation axis which passes through the centerof the sensing surface, during processing to ensure that their sensorsurfaces are coated with a thin film having a spatially uniformthickness profile. Methods and systems of the present invention using asingle rotational planetary system have the advantage of requiring avery simple experimental set up for providing rotation of the substratesundergoing processing.

In another embodiment of this aspect of the present invention, systemsand methods for fabricating a thin film having a uniform physicalthickness profile are provided employing a deposition sensor having awireless transmitter. A device of the present invention for depositingparticles on the receiving surface of a substrate comprises a thin filmdeposition source for generating a flux of particles in a flux region, asubstrate having a receiving surface, a means for translating thesubstrate in the flux region, a sensor comprising a sensing surface forreceiving the flux of particles and a wireless transmitter forgenerating an output signal corresponding to a measurement made by thesensor; a means for translating the sensor in the flux region, and areceiver for receiving the output signal generated by the transmitter.In this embodiment of the present invention, the means for translatingthe substrate translates the receiving surface along a receiving surfacetrajectory in the flux region, and the means for translating the sensormoves the sensing surface along a sensing surface trajectory in saidflux region that is substantially coincident with the receiving surfacetrajectory. This embodiment of the present invention may furthercomprise a thin film deposition source controller in communication withthe receiver for receiving the output signal and controlling operatingconditions of device components of a thin film deposition system such asthe thin film deposition source, shadow mask orientation, target angle,and vacuum chamber geometry. Optionally, substrates and/or depositionsensors of this embodiment of the present invention may also be providedwith means for rotating these elements during translation in the fluxregion.

In one embodiment, the sensor and/or wireless transmitter is selfpowered, for example using a battery power supply, mechanical powersource such as an induction coil or on-board magnetic power source. Thepresent invention includes sensors and/or wireless transmitters that areexternally powered via a wireless connection, such as sensors and/orwireless transmitters that are powered radiatively or magnetically. Useof a wireless transmitter that is self powered via an onboard powersource such as a battery or powered wireless connection is beneficial inthe present invention because it eliminates the need for maintainingdirect electrical contact with measurement circuitry, power suppliesand/or a thin film deposition system controller, which are typicallylocated outside a vacuum deposition chamber housing the thin filmdeposition source, substrate undergoing processing and depositionmonitor. This feature of the present invention has important practicalsignificance with respect to the design and operation of thin filmdeposition systems and methods of using thin film deposition systems ofthe present invention. First, elimination of the need for directelectrical contact with the deposition sensor greatly simplifies thedesign of systems of the present invention because output signals may betransmitted from the sensor and power may be conducted to the sensorwhen it is moving and/or positioned in any orientation in a flux regionof a thin film deposition system. Second, elimination of the need fordirect electrical contact with the deposition sensor allows depositionsensor configurations capable of movement along virtually any trajectoryin the flux region of a thin film deposition system. Third, use of awireless transmitter permits substrate and sensor trajectories to beprovided using conventional mechanical means compatible with highthroughput fabrication, such as single stage and multiple stage rotatingplanetary systems. Fourth, use of a wireless transmitter in the presentinvention provides a means of continuous communication with a receiver,thereby allowing continuous data transmission to a receiver at hightransmission rates. Finally, use of on board, isolated circuitry forreading and transmitting sensor readings, such as the frequency of aquartz crystal microbalance, is significantly less susceptible to noiseand electrical fluctuations, such as fluctuations in capacitance,conductance, resistance and impedance, than sliding contact or rotatingcontact orientations.

Wireless transmitters useful for the thin film deposition systems andmethods of the present invention comprise any device or device componentcapable of transmitting an output signal from the deposition environmentof the sensor and substrate, such as a vacuum chamber, to a receiver,additional measurement circuitry and/or a thin film depositioncontroller without use of direct electrical contact (e.g. a wire,brushes or equivalent sliding or transient electrical connectors). Insome embodiments, the wireless transmitter is an optical element capableof generating an output signal comprising electromagnetic radiationhaving selected frequencies and amplitudes, such as radio frequencywaves, infrared light or visible light, which is received by a fixedreceiver, which is positioned outside the deposition environment.Receivers useful in this aspect of the present invention may compriseantenna and photosensors, such as photodiodes, thermal type infrareddetectors, semiconductor type detectors, photoconductive detectors, andphotomultipliers. Wireless transmitters preferred for some applicationshave low spurious emissions, have low power/current consumptionrequirements and high frequency stability and are capable of fast datatransmission rates. Wireless transmitters and receivers of the presentinvention are optionally capable of multichannel transmission andreception. In a preferred embodiment providing multichannel capability,wireless transmitters and receivers are operated such that cross talk isavoided, for example via encoding means well known in the art ofwireless transmission.

In another aspect, the present invention provides thin film layermonitoring and control methods for determining deposition times and/orthin film deposition source operating conditions in a thin filmdeposition system. Methods of this embodiment of the present inventionmeasure physical and/or chemical characteristics of a thin filmdeposited on a sensing surface of a movable sensor that is moved along atrajectory in a flux region of a thin film deposition system that issubstantially coincident with the trajectory of one or more movablesubstrates undergoing thin film processing. As the movable sensorundergoes a substantially coincident trajectory, the measurementsprovided may be directly related to the physical and chemical propertiesof thin films actually deposited on the substrates. In one embodiment,measurements are carried out in real time by a movable sensor in acontinuous manner and transmitted continuously to a receiver and/or thinfilm deposition controller for data processing, analysis and control ofthe process. Alternatively, the present invention also includesembodiments wherein measurements are periodically or aperiodicallycarried out at discrete and selected deposition times and subsequentlytransmitted to a receiver and/or thin film deposition controller fordata processing, analysis and control of the process.

In one embodiment of the present invention, measurements arecontinuously, periodically or aperiodically obtained during depositionof a thin film, analyzed in real time and used to determine when adeposited thin film has achieved a selected physical thickness and/oroptical thickness. For example, the present invention includes methodswherein the mass of a thin film deposited on the sensing surface of asensor undergoing a trajectory substantially coincident with thetrajectory of receiving surfaces of substrates undergoing thin filmprocessing is measured. Measurements are acquired in real time and usedto calculate the physical thickness of thin films deposited on thesubstrates moving in the flux region. This calculation takes intoaccount the expected density of the deposited thin film and as well thesurface area of the sensing surface. The calculated physical thicknessis compared to a preselected thickness, and used to control the exposuretime of the substrate(s) to precursors in the thin film depositionsystem. For example, upon determining a physical thickness equal to orlarger than the preselected thickness, operating conditions in the thinfilm deposition system are adjusted to stop deposition on the receivingsurfaces of substrates undergoing processing. This can be accomplishedby adjusting the operating conditions of the thin film deposition sourceitself, for example by stopping an ion beam or electron beam in asputtering thin film deposition source, or by introducing a shutter,barrier or mask between the thin film deposition source and thesubstrates that prevents transmission of precursors to the substrate.Alternatively, the present invention also includes embodiments whereinthe optical thickness of a thin film deposited on a sensing surface of asensor undergoing a trajectory substantially coincident with thetrajectory of receiving surfaces of substrates undergoing thin filmprocessing is continuously, periodically or aperiodically measured,compared to a preselected optical thickness, and used to control theexposure times of one or more substrate to precursors. Thin filmmonitoring and control methods of the present invention allow thephysical thickness of a thin film to be selected to within about 0.3%for high-throughput applications. This constitutes an improvement inthickness control over conventional thickness control methods using afixed position sensor equal to about a factor of 10.

In an embodiment useful for fabrication of multilayer structures,measurements of the mass and/or optical thickness of a deposited thinfilm are used to determine when thin film deposition conditions are tobe selectively adjusted to initiate deposition of an additional layer ontop of a previously deposited layer. For example, when a measured orcalculated physical or optical thickness of a first thin film layerhaving a selected first composition is determined to be equal to orgreater than a preselected value, operating conditions of the thin filmdeposition source is adjusted to initiate deposition of an additionalthin film layer having a selected second composition on top of the firstthin film layer. This can be accomplished, for example, by changing thetarget material in a sputtering source or by changing the materialundergoing evaporation in an evaporation source. In this manner, complexstructures may be fabricated using the present techniques comprisingdiscrete thin film layers having well defined and accurate selectedphysical thicknesses and chemical compositions selected with greataccuracy. Use of the thin film layer monitoring and control methods ofthe present invention for making multilayer structures comprising thinfilms is beneficial because these methods provide real time measurementsof thin film properties that do not rely on maintaining a constantsource distribution profile of precursors or characterization of aparts-to-monitor ratio prior to or after thin film processing.Therefore, in contrast to conventional thickness monitoring and controlmethods using a fixed position sensor, the methods of the presentinvention are not limited by uncertainties in the source distributionprofile of precursors.

In another embodiment of the present invention, measurements of thephysical and/or chemical characteristics of a thin film deposited on asensing surface of a sensor moving along a trajectory in the flux regionof a thin film deposition system substantially coincident with thetrajectories of one or more moving substrates undergoing processing isused to provide closed loop feedback control of a physical thin filmdeposition source. The present invention provides methods, for example,wherein successive determinations of the physical thickness or mass of adeposited thin film are used to determine an average observed flux ofprecursors to the receiving surface for a given deposition period. Theaverage observed flux is compared to a preselected flux value, anddeviations from the preselected flux value serve the basis of controlsignals that are used to selectively adjust the thin film depositionsource in a manner establishing and/or maintaining a flux to thereceiving surface equal or within a certain range of the preselectedflux value. In an exemplary embodiment, this control process iscyclically repeated throughout a deposition period. Alternatively, thepresent invention includes methods wherein measurements of themorphology, such as roughness, density, physical state (crystalline,amorphous, semi-crystalline), extent of crystallinity, and/or refractiveindex of a thin film layer deposited on the sensing surface is measuredand used to control operating conditions in a manner to optimize a thinfilm layer morphology and/or refractive index for a given devicefabrication application. In this aspect of the present invention,adjustment of the thin film deposition source on the basis of controlsignals may be achieved by any means known in the art includingselective adjustment of the intensity of an ion beam or electron beam ina sputtering source, selective adjustment of the temperature in anevaporation source, or selective adjustment of the pressure (netpressure and/or partial pressure of oxygen or other bath gas) ortemperature in the deposition chamber. The methods of the presentinvention may also be used to control the average flux of precursorsand/or the source distribution of precursors provided by a thin filmdeposition source

Sensors useful in the present invention provide measurements ofproperties of thin film layers deposited on a sensing surface includingphysical characteristics such as physical thickness, mass, density,morphology (density, physical state, extent of crystallinity), opticalcharacteristics such as refractive index and optical thickness, chemicalcharacteristics such as chemical composition and purity, and electricalcharacteristics such as accumulated electric charge, capacitance,resistance, magnetic hall effect and conductivity. Sensors of thepresent invention are capable of characterizing a thin film layerdeposited directly on a bare receiving surface of a substrate and/or athin film layer deposited on an underlying multilayer structure existingon a substrate. Useful sensors in the present methods include, but arenot limited to, crystal sensors such as quartz crystal microbalancesensors, optical sensors such as single and dual beam opticalinterference sensors, temperature sensors such as thermocouples andthermopiles, and sensors for measuring charge accumulation on thin filmsurface such as an electrometer. Sensors useful in the present inventionalso include position and motion sensors such as accelerometers andoptical position sensors. Sensing surfaces of the present inventioninclude flat surfaces and contoured surfaces, such as, curved, convexand/or concave surfaces. Use of contoured sensing surfaces is useful inapplications of the present invention for processing substrates alsohaving contoured surfaces. In these embodiments, it is often desirableto utilize a contoured sensing surface characterized by the same shape,such as radius of curvature, as a contoured substrate surface undergoingprocessing. For example, use of a sensor having a contoured surface isuseful for depositing one or more thin films on the surface of a lens.

An advantage of embodiments of the present invention having a rotatingquartz microbalance sensor positioned in a flux region is that rotationof the sensing surface during deposition generates a thin film on thesensing surface that has a spatially uniform thickness profile.Thickness uniformity of the thin film layer deposited on the sensingsurface of the quartz crystal microbalance provides a more reliablemeasurement of the mass of material deposited on the sensing surfacebecause such spatially uniform thin film layers generate an isotropicdistribution of stresses on the crystal surface. In contrast, depositionof thin films having a non-uniform thickness profile on the sensingsurface of a quartz crystal microbalance generates anisotropic stressthat can affect different crystal axis and crystal defect sitesdifferently, thereby introducing uncertainties in the mass measurementsprovided under these conditions.

The present invention also includes embodiments wherein the sensorpositioned and moved in the flux region of a thin film deposition systemis capable of simultaneously or near simultaneously measuring aplurality of different thin film characteristics. In one embodiment, forexample, the moveable sensor comprises a plurality of discrete,independent sensors each of which is configured to make a different thinfilm measurement in real time. Sensors of this embodiment can have aplurality of independent sensing surfaces or have a single sensingsurface for making a plurality of measurements. Use of sensors capableof measuring a plurality of thin film characteristics is preferred forsome device fabrication applications because it can provide a morecomprehensive and detailed picture of thin film deposition conditions,thereby enabling control methods and systems for fabricating thin filmlayers having a plurality of accurately selected physical thicknesses,optical properties and/or chemical characteristics. Further, measurementof a suite of different thin film characteristics provides complementarymeasurements useful for extracting more accurate thin film information.For example, temperature measurements may be used to correct additionalmeasurements of thin film properties, such as quartz crystalmicrobalance mass measurements and optical measurements, that exhibittemperature dependence arising from temperature dependent sensorsthemselves, changes in the temperature of a deposited film ortemperature dependent measurement circuitry.

The present invention also includes embodiments wherein a sensor arrayis provided and moved along a trajectory that is substantiallycoincident with the trajectories of one or more receiving surfaces ofsubstrates undergoing thin film processing, thereby providing aplurality of measurements of one or more thin film characteristicscorresponding to different sensor or sensing surface positions. Sensorarrays may comprise a single device having a plurality of independentsensing surfaces located at different relative positions or may comprisea plurality of independent sensors located at different relativepositions. For example, an embodiment of the present invention providesa sensor array on a sub-planet of a dual rotation planetary system thatrotates about a rotational axis. In this configuration the sensor arrayprovides a plurality of independent sensing surfaces or independentsensors which provide measurements of one or more thin filmcharacteristics, such as the mass or optical thickness of depositedmaterial, which corresponds to different distances from the rotationaxis of the sub-planet carrying the sensor array. Thin film layermonitoring and control methods employing a sensor array are useful forsome device fabrication applications because the physical thicknesses ofthin film layers on a plurality of substrates or positions on a singlesubstrate moving along different trajectories in a flux region of a thinfilm deposition system can be simultaneously monitored in real time.

Rotating and/or translating substrates and deposition sensors of thepresent invention may be moved along virtually any trajectory resultingin deposition of a thin film. This aspect of the present invention isparticularly true of embodiments employing a sensor having a wirelesstransmitter that eliminates the need of maintaining electrical contactduring movement of the sensor. Methods and systems of the presentinvention include embodiments wherein the trajectory of rotating and/ortranslating substrates and deposition sensors is entirely within theflux region of a thin film deposition system. Alternatively, the presentinvention includes embodiments wherein the trajectory of rotating and/ortranslating substrates and deposition sensors intermittently passesthrough a flux region of a thin film deposition system. Trajectoriesuseful in the present invention include a variety of types of motionincluding rotational motion about a single rotational axis, rotationalmotion about a plurality of rotational axes, circular orbital motion,elliptical orbital motion, parabolic motion, linear motion and anycombination of these or non-repetitive motions as determined by analysisof the sensor data themselves.

Thin film layer monitoring and control methods of the present inventionare applicable to any type of deposition source, including physical thinfilm deposition sources and chemical thin film deposition sources.Deposition sources useful in the present methods may have any sourcedistribution profile of precursors including, homogeneous sourceprofiles, inhomogeneous source profiles, Gaussian source profiles,Lorentzian source profiles, elliptical source profiles, square wavesource profiles and any combination of these, for example.

The thickness monitoring and control methods of the present inventionare equally applicable to systems, methods and processes for removingmaterial from a substrate surface or coated substrate surface, such aschemical etching, ion beam etching and electron beam etching processes.In one embodiment, a sensor is provided comprising a sensing surfacehaving an exposed coating comprising a thin film layer of a selectedmaterial. Substrates undergoing material removal and the sensor having acoated sensing surface are moved along substantially coincidenttrajectories in a material removal region, such as a region havingchemical etchants present. Continuous, periodic or aperiodicmeasurements of the mass of the exposed thin film layer on the sensingsurface, for example, may be used to provide measurements of the amountof material removed from the sensing surface at a given time and theaverage rate of material removal for a given time interval. If thetrajectories of the sensor and substrate are substantially coincident,these measurements may be directly related to material removal processesoccurring on the substrate surface themselves. This process may be used,therefore, to control exposure times of the substrates to etchantsneeded to achieve a desired extent of material removal or a desiredphysical thickness of a substrate or thin film on a substrate. Thepresent methods may also be used to assess chemical or physical changesof thin films undergoing thin film processing, such as thin filmsundergoing annealing or doping processing steps.

The thin film deposition systems and methods of the present inventionare applicable to a wide range of thin film deposition systems,including ion beam and magnetron sputtering systems, chemical thin filmdeposition systems, and electron beam and thermal evaporation depositionsystems. The present devices and methods are applicable to processingsemiconductor materials by controlling doping and/or ion implantationprocess steps. The methods and devices of the present invention may beused to fabricate thin films and multilayer structures comprising a widerange of materials, such as dielectric materials such as metal oxides,metalloid oxides and salts, semiconductors, conductors such as metalsand metalloids, and materials such as polymers. Methods and devices ofthe present invention may be used to fabricate a variety of thin filmoptical devices including, but not limited to, Fabry Perot elatons,multicavity optical interference filters, lenses, lens coatings,antireflection coatings, partially reflective reflectors, highlyreflective reflectors, polarization selective coatings, and phaseadjustment coatings. Additionally, the methods and devices of thepresent invention are also applicable to fabrication of a wide varietyof other thin film devices including, semiconductor devices, integratedelectronic circuits, and microelectronic devices such as thin filmtransistors, nanoelectronic devices, microfluidic and nanofluidicsystems, light emitting diodes, photodiodes, organic light emittingdiodes, and field effect transistors.

The reduction of errors in process control by monitoring the depositionon a path that is substantially coincident with the path of the parts tobe coated enables further reduction of errors that would be obscured bylarger errors caused by the time-variation of the part-monitor ratio ina system based on a fixed monitor. This invention describes furtherreduction in errors in layer thickness control, by combining a quartzcrystal monitor that follows a path that is substantially coincidentwith the path of the parts, with further improvements of film thicknessmeasurements based on using a temperature-compensated SC-cut quartzcrystal microbalance. An electrical circuit is described that performsthe frequency measurement of two or several modes of oscillation of thecrystal.

In another aspect, the present invention comprises a method formonitoring processing of a thin film on a substrate comprising the stepsof: (a) providing a thin film deposition source for generating a flux ofprecursors in a flux region; (b) providing a substrate having areceiving surface for receiving the precursors; (c) providing a sensorhaving a sensing surface for receiving the precursors; (d) rotating thesubstrate about a first rotational axis; (e) rotating the sensor about asecond rotational axis; (f), translating the rotating substrate in theflux region, wherein rotation and translation of the substrate moves thereceiving surface along a receiving surface trajectory in the fluxregion; (g) translating the rotating sensor in the flux region, whereinrotation and translation of the sensor moves the sensing surface along atrajectory in the flux region that is substantially coincident to thereceiving surface trajectory; and (h) making a measurement of a physicalor chemical property of a thin film on the sensing surface of thesensor, thereby monitoring processing of the thin film on the substrate.

In another aspect, the present invention provides a method forcontrolling the physical thickness of a thin film deposited on asubstrate comprising the steps of: (a) providing a flux of precursors ina flux region; (b) providing a substrate having a receiving surface forreceiving the precursors; (c) providing a sensor comprising a sensingsurface for receiving the precursors; (d) translating the substrate inthe flux region, wherein translation of the substrate moves thereceiving surface along a receiving surface trajectory in the fluxregion; (d) translating the sensor in the flux region, whereintranslation of the sensor moves the sensing surface along a trajectoryin the flux region that is substantially coincident to the receivingsurface trajectory; (e) determining an observed mass of a thin filmdeposited on the sensing surface of the sensor; (f) calculating aphysical thickness of the thin film deposited on the sensing surfacecorresponding to the observed mass; (g) comparing the calculatedphysical thickness to a preselected thickness; and (h) stopping the fluxof precursors in the flux region when the calculated physical thicknessis equal to or greater than the preselected thickness.

In another aspect, the present invention provides a method forcontrolling the thickness of a thin film deposited on a substratecomprising the steps of: (1) providing a flux of precursors in a fluxregion, (b) providing a substrate having a receiving surface forreceiving the precursors; (c) providing a sensor comprising a sensingsurface for receiving the precursors; (d) translating the substrate inthe flux region, wherein translation of the substrate moves thereceiving surface along a receiving surface trajectory in the fluxregion; (e) translating the sensor in the flux region, whereintranslation of the sensor moves the sensing surface along a trajectoryin the flux region that is substantially coincident to the receivingsurface trajectory; (f) determining an observed optical thickness of athin film deposited on the sensing surface of the sensor, (g) comparingthe observed optical thickness to a preselected optical thickness; and(h) stopping the flux of precursors in the flux region when the observedoptical thickness is equal to or greater than the preselected opticalthickness.

In methods of this aspect of the present invention, the step (h) ofstopping the flux of precursors to the receiving surface may comprise(i) the step of positioning a shutter between the thin film depositionsource and the receiving surface of the substrate, (ii) the step ofturning off the thin film deposition source, (iii) the step of turningoff the ion beam and (iv) removing the receiving surface from the fluxregion. Methods of this aspect of the present invention may furthercomprise the step of providing a shadow mask between the thin filmdeposition source and the receiving surface of the substrate, andoptionally the shadow mask may at least in part establish the sourcedistribution profile of precursors in the flux region.

In another aspect the present invention provides a device for processinga thin film on a substrate, the device comprising: (i) a thin filmdeposition source for generating a flux of precursors in a flux region;(ii) a means for translating the substrate having a receiving surfacefor receiving the precursors; wherein translation of the substratesmoves the receiving surface along a receiving surface trajectory in theflux region;(iii) a sensor comprising a sensing surface for receivingthe precursors and a wireless transmitter for generating an outputsignal corresponding to a measurement made by the sensor; (iv) a meansfor translating the sensor, wherein translation of the sensor moves thesensing surface along a sensor trajectory in the flux region that issubstantially coincident with the receiving surface trajectory; and (v)a receiver for receiving the output signal. In one embodiment of thisaspect of the present invention, rotation and translation of thesubstrate the sensor results in substantially the same average fluxes ofprecursors to the receiving surface and the sensing surface for aselected deposition time. In another embodiment of this aspect of thepresent invention, the receiving surface of the substrate and thesensing surface of the sensor simultaneously receive fluxes ofprecursors. In another embodiment of this aspect of the presentinvention, the thin film monitoring and control device further comprisesa thin film deposition source controller in communication with thereceiver for receiving the output signal, wherein the thin filmdeposition source controller controls the flux of precursors in the fluxregion. In another embodiment of this aspect of the present invention,the wireless transmitter generates an output signal comprising infraredradiation, radio waves or both. In another embodiment of this aspect ofthe present invention, the sensor is a mass sensor for measuring themass of precursors deposited on the sensing surface, such as a quartzcrystal monitor. In another embodiment of this aspect of the presentinvention, the sensor is selected from the group consisting of: anoptical thickness monitor for measuring the optical thickness of a thinfilm of precursors on the sensing surface; a temperature sensor formeasuring the temperature of the sensing surface; a refractive indexmonitor for measuring the refractive index of a thin film of precursorson the sensing surface; an electrometer for measuring the electriccharge of a thin film of precursors on the sensing surface; and anaccelerometer for measuring the acceleration of the rotating sensor. Inanother embodiment of this aspect of the present invention, the meansfor translating the rotating substrate and the means for translating therotating sensor comprise a central planet of a dual rotation planetarysystem, wherein rotation of the central planet moves the rotatingsubstrate and the rotating sensor in an orbit about a central rotationalaxis of the dual rotation planetary system, wherein the first and secondrotational axes are positioned the same distance from the centralrotational axis, wherein the means for rotating the substrate is asubstrate sub-planet of the dual rotation planetary system, whereinrotation of the substrate sub-planet rotates the receiving surface aboutthe first rotational axis, and wherein the means for rotating the sensoris a sensor sub-planet of the dual rotation planetary system, whereinrotation of the sensor sub-planet rotates the sensing surface about thesecond rotational axis.

The present invention provides a method for additional reduction ofprocess errors by combining the use of a monitor that follows a path(position and orientation) that is substantially coincident with thepath of parts to be processed, thereby eliminating or reducing processerrors due to a fluctuating parts-to-monitor ratio, with corrections ofthe sensor for environmental effects such as temperature and stress.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a schematic drawing of a thin film layer monitoring system ofthe present invention employing a dual rotation planetary system. FIG.1B shows a schematic diagram illustrating a top plan view of a thin filmlayer monitoring and control system of the present invention having ashadow mask.

FIG. 2 shows an exemplary epitrochoid trajectory of a point on asubstrate or sensor generated by a dual rotation planetary system. The xand y axis in FIG. 2 are in units of centimeters.

FIG. 3 shows an exemplary spatial distribution profile of precursorsgenerated by an ion sputtering thin film deposition source. Contourlines of equal flux (in arbitrary units) are shown. X and Y axes are inunits of centimeters.

FIG. 4A shows a plot of thin film thickness uniformity as a function ofradial position for deposition conditions without a shadow mask presentand FIG. 4B shows a plot of thin film thickness uniformity as a functionof radial position for deposition conditions with a shadow mask present.

FIG. 5 provides a schematic drawing illustrating an embodiment of thepresent invention providing accurate layer thickness control having asensor that is a quartz crystal microbalance sensor positioned on onesubplanet of a dual rotation planetary system.

FIG. 6A provides a schematic diagram of an exploded view of a housingelement for a deposition sensor of the present invention. FIG. 6Bprovides a schematic diagram of a cross sectional side view of sensor adeposition sensor of the present invention.

FIG. 7 shows a schematic diagram illustrating operation of an exemplarylayer thickness control method for controlling thin film processingusing an ion beam sputtering source and a quartz crystal microbalancesensor.

FIG. 8A provides a schematic diagram illustrating a sensor deviceconfiguration wherein a plurality of sensors are positioned on asub-planet that rotates about sub-planet rotational axis. FIG. 8Bprovides a schematic diagram illustrating an alternative sensor deviceconfiguration wherein a plurality of sensors are positioned such thattheir sensing surfaces are positioned at different distances fromsub-planet rotational axis along sensor axis.

FIG. 9A shows a schematic diagram illustrating a side view of a moveableoptical sensor of the present invention for positioning on a means fortranslating the sensor in the flux region of a thin film processingsystem. FIG. 9B is a schematic diagram illustrating a side view of amoveable optical sensor capable of spatially characterizing thin film(s)deposited on the external surface of a sensing substrate.

FIG. 10 shows a block diagram of an electronic circuit for monitoringthe resonant frequencies of two (or several) modes of a quartzmicrobalance crystal.

FIGS. 11A and 11B shows the process improvements of the monitor based onthe SC-cut quartz crystal with temperature corrections as described inthe previous paragraph, compared to the monitor based on the AT-cutquartz crystal. FIG. 11A corresponds to deposition control provided byan AT-cut quartz crystal microbalance and FIG. 11B corresponds todeposition control provided by an SC-cut quartz crystal microbalance.

DETAILED DESCRIPTION OF THE INVENTION

Referring to the drawings, like numerals indicate like elements and thesame number appearing in more than one drawing refers to the sameelement. In addition, hereinafter, the following definitions apply:

“Source distribution profile of precursors” refers to spatialdistributions of the fluxes, concentrations and/or energies ofprecursors. In this context, flux refers to the number of precursorscrossing a unit area per unit time, and may be expressed in units of:(number of precursors) cm⁻²s⁻¹. Source distribution profiles may beexpresses in one, two or three spatial dimensions. Source distributionprofiles may be homogeneous wherein the fluxes, concentrations and/orenergies of precursors are substantially the same for all points on areceiving surface or may be inhomogeneous wherein the fluxes,concentrations and/or energies of precursors are not substantially thesame for all points on a receiving surface.

“Thin film processing” refers to deposition, removal and/or manipulationof materials on a substrate. Thin film processing includes physical thinfilm deposition of thin films, chemical thin film deposition of thinfilms, doping thin films with impurities, changing the composition ofthin films, changing the physical structure or physical state of thinfilms, annealing thin films and removal of material from thin films andsubstrates, for example by etching.

“Precursor” refers to materials generated by a thin film depositionsource and comprises particles such as atoms, molecules, ions,electrically charged particles, particles having no electric charge andany clusters, aggregates or combinations of these materials. In someapplications, precursor also refers to electrons generated by a thinfilm deposition source or material removal system, such as an electronbeam etching system. Thin films can be processed using the presentmethods by a variety of physical and chemical processes involvingprecursors including, but not limited to, condensation of precursors ona substrate surface , nucleation of phase changes of precursors on asubstrate surface, chemical reaction of precursors on a substrate,adhesion of a precursor to a substrate

“Flux region” refers to a region of a thin film deposition system havingprecursors present. Thin film layers are deposited onto a substrate in athin film deposition system by positioning the substrates in a fluxregion. In the present invention, substrates and deposition sensors arepositioned and moved in a flux region during processing of a thin film.In some embodiments, the flux region of a thin film deposition system islocated within a vacuum chamber.

“Thin film deposition source” refers to a device or device component forgenerating precursors for thin film processing. Thin film depositionsources useful in the methods and devices of the present inventioninclude, but are not limited to, physical thin film deposition sourcessuch as ion beam and electron beam sputtering sources, magnetronsputtering sources, chemical evaporation sources, thermal evaporationsources, and chemical thin film deposition sources such as plasmaenhanced chemical thin film deposition sources, thermal chemical thinfilm deposition sources, and ultra high vacuum chemical thin filmdeposition sources.

“Process source thickness factor” refers to the path integral$\begin{matrix}{{{T_{\overset{\rightharpoonup}{p}}\left( {t_{1},t_{2}} \right)} = {\int_{t_{1}{\overset{\rightharpoonup}{p}{(t)}}{\overset{\rightharpoonup}{n}{(t)}}}^{t_{2}}{{R\left( {{\overset{\rightharpoonup}{p}(t)},{\overset{\rightharpoonup}{n}(t)},t} \right)}\quad{\mathbb{d}t}}}},} & (I)\end{matrix}$where {overscore (p)}(t) is the time-dependent trajectory (path) of thesubstrate or sensor, {overscore (n)}(t) is the time-dependent normalvector of the substrate or sensor as it follows the trajectory,R({overscore (p)}(t),{overscore (n)}(t),t) is the number of precursorsper second that will act on the substrate or sensor (e.g. will stick fora deposition process) at the point {overscore (p)}(t) and orientation(surface normal) {overscore (n)}(t), at time t, and t₁ and t₂ arebeginning and end times.

For a time-dependent quantity, f(t), the statistical mean, denoted{f(t)}_(t), refers to the average of f(t) over a time period that islong compared to the process time.

The time scale for changes in the deposition rate on the part or monitordue to motion of the trajectory is Δt_(motion)=min(R/|d{overscore(r)}/dt|,1/d{circumflex over (n)}/dt|), where R is the characteristicwidth of the deposition beam. Source fluctuations on time scales muchsmaller than this are not of significance because the depositedthickness is the same as from a steady source with a deposition ratethat is the average deposition rate over many of these very rapidfluctuations. Over time scales on the order of or greater thanΔt_(motion), however, gradual changes in the source rate could lead tosignificant process errors, for example if one does not monitor theprogress of the layer thickness during deposition but instead choose afixed stop time based on the previously measured deposition rate. Wewill call this larger time scale the characteristic time of sourcefluctuations, and it is defined as follows.

Consider a layer deposited for a layer time Δt_(L) on two parts (or apart (i.e. substrate) and a monitor) that follow identical trajectories,but one occurring at a time displaced by ≢t. The fractional differencein thickness of these two parts is:$\frac{\Delta\quad{T\left( t\rightarrow{t + {\Delta\quad t}} \right)}}{T} \equiv {\left\{ {{\int_{t}^{t + {\Delta\quad t_{L}}}{{R\left( {{\overset{\rightharpoonup}{r}\left( {t + {\Delta\quad t}} \right)},{\hat{n}\left( {t + {\Delta\quad t}} \right)}} \right)}\quad{\mathbb{d}t}}} - {\int_{t}^{t + {\Delta\quad t_{L}}}{{R\left( {{\overset{\rightharpoonup}{r}(t)},{\hat{n}(t)}} \right)}\quad{\mathbb{d}t}}}} \right\}/{\int_{t}^{t + {\Delta\quad t_{L}}}{{R\left( {{\overset{\rightharpoonup}{r}(t)},{\hat{n}(t)}} \right)}\quad{{\mathbb{d}t}.}}}}$

The characteristic time of source fluctuations is the smallest timedisplacement (Δt) for which${\sqrt{\left\langle \left( \frac{\Delta\quad{T\left( t\rightarrow{t + {\Delta\quad t}} \right)}}{T} \right)^{2} \right\rangle} = A},$where A is a tolerance on the layer thickness errors (e.g. 0.5%).

In words, the characteristic time of source fluctuations is the timedisplacement for which the difference in the layer thickness created atdisplaced times but identical trajectories typically or statistically(RMS) exceeds the tolerance on layer thickness errors. This time scaleis typically about 5 minutes in IBS film coating chambers for atolerance of 0.5%.

There are other similarly applicable ways to define the characteristictime of source fluctuations, for example in terms of the decay of acorrelation function involving the layer thickness for two identicaltrajectories that are displaced in time.

“Coincident trajectories” refer to the motion of two or more moveabledevices or device components, such as substrates and deposition sensorsthat are coincident with respect to time and space. Coincidenttrajectories pass through the same points in space at similar times. Atrajectory coincident with another trajectory may provide a pathidentical to the path of the other trajectory, may provide a componentof its path that overlaps a portion or all of the path of the othertrajectory, or may provide a path that fully encompasses the path of theother trajectory in addition to having an additional nonoverlappingcomponent of its path. Coincident trajectories useful in the presentinvention may be cyclical or noncyclical. Coincident trajectories usefulin the present invention may be entirely contained within a flux regionof a thin film deposition system or may intermittently pass through theflux region of a thin film deposition system. The term “substantiallycoincident trajectories” is intended to encompass some deviations fromabsolute temporal and spatial coincidence of two or more trajectories.In one aspect, substantially coincident trajectories deviate fromabsolutely coincidence by less than 2 centimeters, per cyclicallytrajectory. In another aspect, substantially coincident trajectories oftranslating and/or rotating substrates in a flux region providesubstantially the same average fluxes of precursors for a selecteddeposition interval. In another aspect, the controlled processingdetermines a stop time (i.e. end point of thin film processing timeinterval) by continuous time monitoring of the process source thicknessfactor function on the trajectory of a sensor that follows a path thatis substantially coincident with the substrate being processed. For agiven target process accuracy A (for example in a deposition processdescribed here this is the tolerance in fractional accuracy of the layerthickness values, typically A=0.5%), we define two trajectories to besubstantially coincident over the layer time Δt_(L) if: $\begin{matrix}{{\left\lbrack \left\langle \left( \frac{{T_{{\overset{\rightharpoonup}{p}}_{2}}\left( {t,{t + {\Delta\quad t_{L}}}} \right)} - {T_{{\overset{\rightharpoonup}{p}}_{1}}\left( {t,{t + {\Delta\quad t_{L}}}} \right)}}{T_{{\overset{\rightharpoonup}{p}}_{1}}\left( {t,{t + {\Delta\quad t_{L}}}} \right)} \right)^{2} \right\rangle_{t} \right\rbrack^{1/2} < A},} & ({IIIa})\end{matrix}$

Two trajectories (or two paths) are also defined to be substantiallycoincident if on a smaller time interval, Δt_(c), if $\begin{matrix}{{\left\lbrack \left\langle \left( \frac{{T_{{\overset{\rightharpoonup}{p}}_{2}}\left( {t,{t + {\Delta\quad t_{c}}}} \right)} - {T_{{\overset{\rightharpoonup}{p}}_{1}}\left( {t,{t + {\Delta\quad t_{c}}}} \right)}}{T_{{\overset{\rightharpoonup}{p}}_{1}}\left( {t,{t + {\Delta\quad t_{c}}}} \right)} \right)^{2} \right\rangle_{t} \right\rbrack^{1/2} < A^{\prime}},} & ({IIIb})\end{matrix}$for a different threshold A′ (usually larger than A ) where it can beshown by theory or by measurements, and by statistical analysis, thatthis condition (IIIa) is true.

For example, if the process accuracy goal is A=0.3% and Δt_(L)=30minutes, then two trajectories are substantially coincident over a timescale Δt_(c)=3 minutes if their path integrals differ in RMS by 2%, andit can be shown that this 2% RMS difference in thickness on the 3 minuteinterval implies that the RMS difference in thickness for the twotrajectories will be less than 0.3% for a full 30 minute layerdeposition.

“Thickness profile” refers to a one or two dimensional spatialdistributions of the physical or optical thicknesses of a thin film orplurality of thin film layers on a receiving area of a substrate or asensing surface of a sensor. The present invention provides methods offabricating thin films having uniform thickness profiles and thin filmshaving selected non-uniform thickness profiles

“Substantially the same average fluxes of precursors” refers to fluxesof precursors to two or more surfaces during a selected deposition timethat result in formation of thin films having physical thicknessesand/or optical thicknesses that are with 1 % of each other, preferablyfor some applications are with 0.5% of each other and more preferablyfor some applications are with 0.25% of each other

“Thin film layer” refers to a thin film comprising a coating of atoms,molecules or ions or mixtures and/or clusters thereof. Thin film layersin the present invention may comprise a single-layer having asubstantially constant composition, a single layer having a compositionwhich varies as a function of physical thickness or a plurality of thinfilms layers. Thin film layers useable in the present invention may haveeither a homogeneous composition or a heterogeneous composition and maycomprise a single phase or a plurality of phases. Thin film layers ofthe present invention include but are not limited dielectric materials,semiconductors, conducting materials, organic materials such as polymersand any combinations of these materials. In a preferred embodiment,reference to thin dielectric layers in the present invention includesbut is not limited to metal oxide, metalloid oxide and salt thin films.Metal oxides, metalloid oxides and salts useable in the presentinvention include, but are not limited to, Ag, Au, Ta₂O₅, SiO₂, HfO₂,TiO₂, MgF₂, AlO₂, CaF₂, Nb₂O₅, glass or mixtures of these materials.Thin metalloid and metal layers of the present invention include but arenot limited to Si and Al. Thin film layers of the present invention mayhave any size, shape, physical thickness or optical thickness suitablefor a selected application.

“Optical thickness” refers to the effective path length of light thattakes into consideration the refractive index of the material light ispropagating through. Analytically, optical thickness and optical pathlength terms may be expressed in the following summation as the productof physical thickness and the refractive index of a layer or pluralityof layers: $\begin{matrix}{{{{optical}\quad{thickness}} = {{{optical}\quad{path}\quad{length}} = {\sum\limits_{x}{n_{x} \times L_{x}}}}},} & {IV}\end{matrix}$where L_(x) is the physical thickness of region x and n is therefractive index of region x. Equation IV is applicable to structurescomprising single layers, partial layers and multilayer structures.

“Operably connected” and “operably coupled” are used synonymously in thepresent description and refer to a configuration of two or more deviceelements such that they can be used in combination to achieve specificfunctions, operations, functional tasks or device capabilities/featuresin a particular device configuration. Operably connected device elementscan be optically coupled, electronically coupled, electrically coupled,mechanically coupled and magnetically coupled or any combination ofthese. Operably connected device elements can be in one waycommunication, in two way communication or any combination of thesedevice configurations. Operably coupled device elements is used in thepresent invention to provide devices and device configurations having adesired functionality, such as fabrication of spatially uniform thinfilms and devices comprising thin films having accurately selectedphysical and/or optical thicknesses, thickness profiles, chemicalproperties and optical characteristics.

“Spatially uniform films”, “thin films having spatial uniformity” and“thin films having a uniform thickness profile” are used synonymously inthe present description and refer to thin films having a physicalthickness that is substantially constant over a selected thin film area.In one embodiment, spatially uniform films exhibit deviations from anaverage physical thickness per unit area equal to or less than 0.25%over an area defined by a 10 inch diameter.

“Translation” refers to movement of a device or device component, suchas a substrate or deposition sensor. Translation may comprise any typeof motion including, but not limited to, rotational motion about asingle rotational axis, rotational motion about a plurality ofrotational axes, circular orbital motion, elliptical orbital motion,parabolic motion, linear motion and any combination of these.

“Part” and “substrate” are used synonymously in the present descriptionand refer to elements, materials, surfaces, device components anddevices undergoing thin film processing.

In the following description, numerous specific details of the devices,device components and methods of the present invention are set forth inorder to provide a thorough explanation of the precise nature of theinvention. It will be apparent, however, to those of skill in the artthat the invention can be practiced without these specific details.

This invention provides methods and devices for fabricating thin filmlayers and multilayer structures comprising a plurality of thin filmlayers exhibiting good spatial uniformity. Particularly, the presentinvention provides film thickness monitoring and control methods andsystems which allow the physical thickness, thickness profile, chemicalcomposition and optical properties of deposited thin films to beselected within improved accuracy and precision relative to conventionmonitoring and control methods and systems employing a fixed positionsensor.

FIG. 1A is a schematic drawing of a thin film layer monitoring andcontrol system of the present invention employing a dual rotationplanetary system. As shown in FIG. 1A, the thin film monitoring system100 comprises a dual rotation planetary system 105 having a centralrotating platform 110 and a plurality of rotating sub-planets 115A,115B, 115C and 115D. Central rotating platform 110 is configured torotate about central rotational axis 120 (as shown by arrow proximate tocentral rotational axis 120) and rotating sub-planets 115A, 115B, 115Cand 115D are configured to rotate about first, second, third and fourthrotational axes 117A, 117B, 117C and 117D, respectively (as shown byarrow proximate to rotational axes 117A, 117B, 117C and 117D). Substrate130 undergoing thin film processing is affixed to rotating sub-planet115A and sensor 135 is affixed to rotating sub-planet 115C. Substrate130 has a receiving surface 140 for receiving particles in a flux regionof a thin film deposition system and sensor 135 has a sensing surface145 and a wireless transmitter 150. Wireless transmitter 150 is capableof generating output signals corresponding to measurements made bysensor 135 and transmitting these output signals to a fixed positionreceiver 155. In FIG. 1A, the transmission of output signals isschematically illustrated by arrow 160. Optionally, receiver 155 may beoperably connected to thin film deposition system controller 166 capableof receiving output signals, calculating thin film properties, andcontrolling operating conditions and device components of a thin filmdeposition system, such as a thin film deposition source, the netpressure, partial pressure of O₂ or other bath gas, and/or thetemperature in a thin film deposition system and the rotationalvelocities of the central planet and sub-planets. In this embodiment,thin film deposition system controller 166 is operably connected to athin film deposition system or component thereof, such as a thin filmdeposition source, a thin film deposition chamber and/or dual rotationplanetary system 105.

As shown in FIG. 1A, first, second, third and fourth rotational axes117A, 117B, 117C and 117D are positioned at about the same distance fromcentral rotational axis 120. Rotation of central rotating platform 110,in this configuration, results in movement of each of rotatingsub-planets 115A, 115B, 115C and 115D in a circular orbit about centralrotational axis 120. Optionally, substrate 130 is positioned a distancefrom first rotational axis 117A substantially equal to the distance thatsensing surface 145 is positioned from third rotational axis 117C. In auseful embodiment of the present invention providing enhanced thicknesscontrol of thin film layers deposited on receiving surface 140, first,second, third and fourth rotational axes 117A, 117B, 117C and 117D arepositioned about 15 centimeters from central rotational axis 120,receiving surface 140 is position about 4 centimeters from firstrotational axes 117A, and sensing surface is position about 4centimeters from third rotational axes 117C.

To provide thin film layer control, thin film monitoring and controlsystem 100 is positioned, at least partially, within the flux region ofa thin film deposition system having precursors therein. During exposureto precursors in the flux region, central rotating platform 110 isrotated about central rotational axis 120 and rotating sub-planets 115A,115B, 115C and 115D are rotated about first, second, third and fourthrotational axes 117A, 117B, 117C and 117D, respectively. In anembodiment of the present invention providing thin films having goodspatial uniformity, rotating sub-planets 115A, 115B, 115C and 115Drotate about their respective rotational axes at the same rotationalvelocity. In an exemplary embodiment, the central rotating platform 110rotates about central rotational axis 120 at a rotational velocity ofabout 60 rotations per minute to about 100 rotations per minute, androtating sub-planets 115A, 115B, 115C and 115D rotate about theirrespective rotational axes at rotational velocities of about 120rotations per minute.

Rotation of central rotating platform 110 and rotating sub-planets 115A,115B, 115C and 115D is preferably carried out simultaneously for aselected deposition period thereby generating epitrochoid trajectoriesof receiving surface 140 of substrate 130 and sensing surface 145 ofsensor 135. FIG. 2 shows an exemplary epitrochoid trajectory generatedby a dual rotation planetary system. Receiving surface 140 and sensingsurface 145 are moved through a plurality of completed cyclicalepitrochoid trajectories during deposition of a thin film layer.Simultaneous rotation of central rotating platform 110 and sub-planets115A, 115B, 115C and 115D moves receiving surface 140 and sensingsurface 145 through substantially coincident cyclical trajectories inthe flux region, thereby exposing these components to substantiallysimilar net deposition conditions over the selected deposition period.In one embodiment, for example, simultaneous rotation of centralrotating platform 110 and sub-planets 115A, 115B, 115C and 115D exposesthe sensing surface 145 and receiving surface 140 to similarconcentrations of precursors in a given source distribution ofprecursors for similar time periods. The use of substantially coincidentreceiving surface and sensing surface trajectories is particularlyuseful in embodiments wherein the rate of completing a cyclicaltrajectory is on the same time scale or faster than the characteristictime of source fluctuations. Further, use of substantially coincidentreceiving surface and sensing surface trajectories is particularlyuseful in embodiments wherein the rate of completing a cyclicaltrajectory is fast enough such that receiving surface and sensingsurfaces accumulate thin films having substantially the same thicknesses(e.g. within 0.3%).

Deposition, condensation and/or reaction of precursors on sensingsurface 145 and receiving surface 140 results in formation and growth ofthin film layers on these components as they are moved along coincidenttrajectories in the flux deposition region. Preferably, the trajectoriesof these components are such that thin film layers having substantiallythe same physical properties such as physical thickness, chemicalcharacteristics such as chemical composition, and optical propertiessuch as refractive index and optical thickness are generated on sensingsurface 145 and receiving surface 140 in a time scale that is shorterthan the characteristic time of fluctuations in the source distributionprofile (i.e. the characteristic time of source fluctuations). Sensor135 is configured to make periodic or aperiodic, real time measurementsof select physical and/or chemical characteristics of the thin filmlayer on sensing surface 145 and wireless transmitter 150 generatesoutput signals corresponding to these measurements and transmits them toreceiver 155, which may be configured to direct the output signals tothe thin film deposition system controller 166. Output signals areanalyzed in real time by a thin film deposition system controller 166,thereby providing real time determinations of important physicalproperties, chemical characteristics, and optical properties whichdirectly correspond to the thin film layer on receiving surface 140.These determinations serve the basis of control signals generated bythin film deposition system controller 166 which may be used to controldevice components such as the thin film deposition source, operatingconditions of the thin film deposition system such as the temperatureand/or pressure (net pressure or partial pressures of O₂ and/or otherbath gases) of the thin film deposition chamber or any combination ofthese. For example, control signals generated by thin film depositionsystem controller 166 may serve as the basis of control commandsstopping generation of precursors by the thin film deposition source,changing the composition of precursors to initiate deposition of a newthin film layer or providing the basis of closed loop feedback controlof thin film deposition conditions.

Optionally, the thin film layer monitoring an control system of thisaspect of the present invention may further include one or more sourcedistribution-modifying elements, such as shadow masks, positionedbetween the thin film deposition source and the rotating and/ortranslating substrates undergoing processing (and also rotating and/ortranslating sensor). FIG. 1B shows a schematic diagram illustrating atop plan view of a thin film layer monitoring and control system of thepresent invention having a shadow mask. As shown in FIG. 1B, thin filmdeposition source 180 is an ion beam sputtering source comprising asource of ions 181 which generates and ion beam 182 that is directedonto a target 183 having a selected composition. Precursors(schematically illustrated as arrows 184) are generated from theinteraction of ion beam 182 and target 183. Precursors 184 arecharacterized by a first spatial distribution profile 191 (schematicallyrepresented in one spatial dimension) in a region proximate to target183. FIG. 3 shows an exemplary spatial distribution profile ofprecursors generated by an ion beam sputtering thin film depositionsource. Contour lines of equal flux are indicated (in arbitrary units)and horizontal and vertical axes are in units of centimeters.

Precursors 184 are directed to substrates 185 and sensor 186 onsub-planets 187 on central rotating platform 188 of dual rotationplanetary system 189, thereby forming thin film layers on the receivingsurfaces and sensing surface of these components. Shadow mask 190 ispositioned between thin film deposition source 180 and substrates 185and sensor 186, and at least partially prevents transmission of someprecursors from thin film deposition source 180 to substrates 185 andsensor 186. As a result of the presence of shadow mask 190 precursorscharacterized by a second spatial distribution profile 192 are exposedto receiving surface of substrates 185 and sensing surface of sensor186. As shown in FIG. 1B, second spatial distribution profile ofprecursors 192 (schematically represented in one spatial distribution)is different from first spatial distribution profile 191 and ischaracterized by a dip in the intensity of precursors corresponding tothe position of shadow mask 190. Use of a shadow mask in combinationwith substrates 185 and sensor 186 provided on dual rotation planetarysystem 189 provides a means of fabricating spatially uniform thin filmslayers on substrates 185 having an accurately selected thickness.Particularly, use of a shadow mask 190 in this embodiment of the presentinvention establishes substantially the same average fluxes ofprecursors to receiving surfaces of substrates 185 and sensor surfacesof sensor 186 having different radial positions with respect to therotational axes of subplanets 187. Therefore, shadow mask 190 may beviewed as a device component useful for establishing and maintainingcoincident trajectories of substrates and sensors having differentradial positions with respect to the rotational axes of subplanets 187.FIG. 4A shows a plot of thin film thickness uniformity as a function ofradial position for deposition conditions without a shadow mask presentand FIG. 4B shows a plot of thin film thickness uniformity as a functionof radial position (in centimeters) for deposition conditions with ashadow mask present. In FIGS. 4A and 4B, uniformity is defined relativeto the thickness at the center of a rotating subplanet of a dualrotation planetary system, and is expressed by the equation:$\begin{matrix}{{{uniformity} = \left( \frac{T_{x}}{T_{center}} \right)};} & (V)\end{matrix}$wherein T_(x) is the thickness at point x and T_(center) is thethickness at the center of the rotating subplanet. A comparison of FIGS.4A and 4B indicates that incorporation of a shadow mask can be usefulfor fabricating uniform thickness thin film structures on substrateshaving different radial positions. This combination of devicecomponents, therefore, makes the present invention is applicable tohigh-throughput fabrication of single and multilayer thin filmstructures, wherein a plurality of substrates having different radialpositions are processed simultaneously.

FIG. 5 provides a schematic drawing illustrating an embodiment of thepresent invention providing accurate layer thickness control, whereinsensor 135 is a crystal sensor, such as a quartz crystal microbalancesensor that provides measurements in real time of the mass of a thinfilm layer deposited on sensing surface 145. In this embodiment, sensor200 positioned on sub-planet 115C and comprises crystal 205 having asensing surface 210, shield plate 215 having an aperture 220 whichexposes sensing surface 210 to a flux of precursors, wirelesstransmitter 225 and battery power supply 230. Measurement circuitry forcrystal 205 (not shown in FIG. 5) is provided behind shield plate 215 soas to avoid electrical and magnetic interference resulting from electricfields, magnetic fields or both generated in the flux region. In someembodiments, measurement circuitry is preferably compatible with lowpressure environments, such as the low pressure environment of a vacuumsystem. In one embodiment, wireless transmitter 225 is either an IRtransmitter or an RF transmitter. Use of the wireless transmitter 225and battery power supply 230 is useful in this embodiment of the presentinvention because it eliminates the need of establishing electricalcontact between the sensor 200 and any other device component of themonitoring system. Another advantage provided by the compact, selfpowered sensor design shown in FIG. 5 is that the sensor can be poweredfor very long time periods, for example hundreds of hours, that arecompatible with high throughput thin film processing applications.

FIG. 6A provides a schematic drawing showing an exploded view of ahousing element 300 for sensor 200. As shown in FIG. 6A, housing element300 comprises tube element 310, an upper circular element 320 and alower circular element 330. Upper circular element 310 has a crystalhole 322 for exposing sensing surface 210 of crystal 205 and a witnesshole 315 positioned in front of a test substrate which may be evaluatedafter deposition to verify that a selected thin film thickness isactually achieved during deposition. Tube element 310 is large enough tohouse crystal 205, transmitter 225 and battery power supply 230. Lowercircular element 330 has four through holes for fastening screws thatpass through receiving holes in Tube element 310 and terminate in uppercircular element 320. The fastening screw configuration provided securestube element 310 between upper and lower circular elements 320 and 330.The housing design shown in FIG. 6A is capable of securing crystal 205and associated measuring circuitry such that these elements do not movesignificantly during rotation of sub-planet 115C. Lower circular element330 is arranged so that is may be attached to a rotating means (notshown) and, thereby form a sub-planet in a dual planetary rotationsystem. FIG. 6B provides a schematic drawing of a cross sectional sideview of sensor 300 indicating the position of crystal 205, battery 230,crystal measurement circuitry 375, and transmitter 225.

Measurements of the mass of material deposited on sensing surface 210 isachieved in this embodiment of the present invention by monitoringchanges in the fundamental resonance frequency of the crystal 205 uponapplication of an appropriate alternating electric field. In thisembodiment, receiver 225 is configured to transmit output signalscorresponding to the measured resonance frequency of the crystal 205,and thin film deposition system controller 166 is capable of calculatingthe mass of materials deposited on the sensing surface 210. Withknowledge of the surface area of sensing surface 210 and the expecteddensity of the deposited thin film layer, an observed physical thicknessof the thin film layer can be calculated using the measured mass ofdeposited material. The calculated observed physical thickness is usedin layer thickness control methods of the present invention to determinewhen a thin film layer having a desired physical thickness has beenachieved and, thus, identifying the point in time when deposition ofprecursors is to be stopped. For example, thin film deposition systemcontroller 166 may be configured to compare calculated physicalthicknesses to a preselected set point thickness and/or mass, and togenerate command signals for stopping the production of precursors by athin film deposition source upon calculation of a physical thicknessthat is equal to or exceeds the preselected set point thickness and/ormass.

FIG. 7, shows a schematic diagram illustrating operation of an exemplarylayer thickness control method for controlling thin film processingusing an ion beam sputtering source and a quartz crystal microbalancesensor. As shown in FIG. 7, the ion source generates a beam of ionshaving a distribution of ion intensities, which is directed onto thesurface of a target having a selected chemical composition. Precursorsare generated upon interaction with the ion beam and the target, therebyestablishing a source distribution of precursors proximate to thesensing surface of a quartz crystal microbalance sensor. A signal isgenerated by the quartz crystal microbalance sensor that is dependent onthe mass of material present on the sensing surface. In one embodiment,the quartz crystal is provided as a part of a closed feedback loop in anactive oscillator circuit. A frequency counter is operably connected tothe oscillator circuit such that it is capable of counting the number ofoscillations per unit time over a selected time and which converts theoutput signal from the oscillator circuit to a square wave having afrequency representative of the frequency of the quartz crystalmicrobalance output signal. This signal is provided to a microcontrollerwhich encodes the data by conversion into a digital signal. The digitalsignal is provided as input to a wireless transmitter which generates awireless signal that is transmitted to a receiver operably connected toa thin film deposition system controller, such as a computer orprocessor which is capable of running process control software. The thinfilm deposition system controller converts the transmitted signal into amass measurement and determines an observed physical thickness from themass measurement. The thin film deposition system controller is alsocapable of generating command signals based on the observed physicalthickness, which may be used to control device components of the thinfilm deposition system. In the method schematically illustrated in FIG.7, thin film deposition system controller is operably connected to theion beam source and capable of controlling the rate and/or sourcedistribution of ions generated and directed at the target.

As also shown in FIG. 7, the quartz crystal microbalance, activeoscillator circuit, frequency controller, microcontroller and wirelesstransmitter are all provided on a rotating subplanet of a dual planetarysystem. In some applications, providing the crystal measurementcircuitry on the rotating subplanet is particularly useful for providingaccurate mass and/or physical thickness measurements because sliding,moving or rotating electrical contacts to the crystal are avoided.Avoiding use of sliding, moving and/or rotating electrical contacts tothe crystal can eliminate or minimize significant errors in measurementsof the resonance frequency of a quartz crystal microbalance due tochanges in resistance, capacitance, impedance and conductance which areoften are introduced by such motions. As also shown in FIG. 7, thequartz crystal microbalance, active oscillator circuit, frequencycontroller, microcontroller, wireless transmitter, ion beam source andtarget are all provided in a vapor deposition chamber and the receiverand vapor deposition controller are provided outside the vapordeposition chamber.

The present invention also includes methods and algorithms forcontrolling the thickness of thin films deposited on substratesundergoing processing. In an exemplary method, a plurality of real timemeasurements of the frequency (f_(t)) of a quartz crystal microbalanceare provided by the monitoring and control systems of the presentinvention a specified time interval (Δt). These measurements areconverted to a normalized change in frequency (Δf_(normalized)) via theexpression: $\begin{matrix}{{\Delta\quad f_{normalized}} = {\left( \frac{f_{0} - f_{t}}{f_{0}} \right).}} & ({II})\end{matrix}$The calculated normalized change in frequency (Δf_(normalized)) isconverted into physical thickness using an empirically determined lookuptable, function or algorithm. Physical thickness is determined atseveral time intervals during deposition and used in a predictivealgorithm to determine the deposition time required to achieve a desiredthickness. Exemplary predictive algorithms periodically fit a pluralityof experimentally determined physical thickness calculations toascertain an average deposition rate over a selected time intervaluseful for predicting stopping times required for a desired thickness.

Exemplary thin film deposition controllers of the present inventioncomprise computers, computer processors and other hardware equivalents.Exemplary computers useable in the present methods includemicrocomputers, such as a IBM personal computer or suitable equivalentsthereof, and work station computers. In one embodiment of the presentinvention, a thin film deposition controller of the present inventioncomprises a computer capable of running process control software and/oralgorithms for calculating physical, chemical and/or optical propertiesof thin films. As appreciated by one skilled in the art, computersoftware code embodying the methods and algorithms of the presentinvention may be written in any suitable programming language. Exemplarylanguages include, but are not limited to, C, C⁺⁺ or any other versionsof C, Perl, Java, Pascal, or any equivalents of these.

In some sensor configurations, the crystal resonance frequency and themeasurement circuitry for operating the crystal sensor is dependent ontemperature. Accordingly, determination of the mass of a thin filmdeposited on sensing surface 210 is a temperature dependent measurement.Referring again to FIG. 5, to account for this temperature dependence,sensor 200 may further comprise one or more temperature sensors 250, forexample thermocouples or thermopiles, for providing real time, directmeasurements of the temperature of material deposited on sensor 200. Inan alternative embodiment, the temperature of the crystal is indirectlydetermined by monitoring the frequencies of the fundamental and thirdharmonic modes of the crystal. In these embodiments, receiver 225 isconfigured to transmit output signals corresponding to both mass andtemperature measurements, and thin film deposition source controller 160is capable of determining the mass of deposited material corrected forany temperature dependence in the crystal resonance frequency andmeasurement circuitry. Using the measured temperature information, forexample, the resonance frequency can be corrected based on experimentalcalibration data that is measured and analyzed prior to thin filmdeposition.

The present invention includes a number of other sensor configurationsuseful for thin film device fabrication applications. FIG. 8A provides aschematic diagram illustrating a sensor device configuration 500 whereina plurality of sensors 510 are positioned on a sub-planet 520 thatrotates about sub-planet rotational axis 525. As shown in FIG. 8A, thesensing surfaces 530 of the sensors 510 are positioned the same distancefrom sub-planet rotational axis 525. Sensors 510 may comprise the sametype of sensor capable of measuring the same thin film property orsensors 510 may comprise different types of sensors capable of measuringdifferent thin film properties. An advantage of this configuration isthat it includes embodiments wherein a suite of complementary thin filmmeasurements are made and analyzed in real time, thereby allowing forenhanced thin film processing control. FIG. 8B provides a schematicdiagram illustrating an alternative sensor device configuration 600wherein a plurality of sensors 610 are positioned such that theirsensing surfaces 630 are positioned at different distances fromsub-planet rotational axis 625 along sensor axis 630. In thisembodiment, sensors 610 may comprise the same type of sensor capable ofmeasuring the same thin film property or sensors 610 may comprisedifferent types of sensor capable of measuring different thin filmproperties. An advantage of this configuration is that it includesembodiments wherein sensors 610 undergo a plurality of differenttrajectories that are coincident with trajectories of a plurality ofsubstrates having receiving surfaces positioned at different distancesfrom the rotational axis of a sub-planet in a dual rotation planetarysystem.

Referring again to FIG. 1A, the present invention includes embodimentswherein additional substrates 170 are provided on any of sub-planets115A, 115B, 115C and 115D. Additional substrates 170 may be provided onthe same or different sub-planets. Sensor 135 can be provided on its ownsub-planet, as shown in FIG. 1A, or can be provided on a sub-planethaving one or more substrates thereon. Although the embodiment shown inFIG. 1A indicates 4 sub-planets, the methods and devices of presentinvention may be practiced using dual planetary systems having anynumber of sub-planets. Further, the methods and devices of the presentinvention may be practiced using higher order planetary systems, such astriple and quadruple planetary systems. Further, the present inventionincludes embodiments employing a plurality of deposition sensorspositioned on the same or different sub-planets of a planetary system.This aspect of the present invention is particularly useful forproviding measurements of a distribution of precursors for a given thinfilm deposition source that may be used to design shadow masks for agiven application (e.g. determine the physical dimensions of a shadowmask) or to control a dynamic shadow mask.

The terms and expressions which have been employed herein are used asterms of description and not of limitation, and there is no intention inthe use of such terms and expressions of excluding any equivalents ofthe features shown and described or portions thereof, but it isrecognized that various modifications are possible within the scope ofthe invention claimed. Thus, it should be understood that although thepresent invention has been specifically disclosed by preferredembodiments and optional features, modification and variation of theconcepts herein disclosed may be resorted to by those skilled in theart, and that such modifications and variations are considered to bewithin the scope of this invention as defined by the appended claims.The specific embodiments provided herein are examples of usefulembodiments of the present invention and it will be apparent to oneskilled in the art that the present invention may be carried out using alarge number of variations of the devices, device components, methodssteps set forth in the present description. Methods and devices usefulfor the present methods can include a large number of optional deviceelements and components including, pressure monitoring devices,temperature monitoring devices, substrate translators and rotators,vacuum systems and vacuum chambers, valves, pumps, lasers, temperaturecontrollers, photodetectors, heating elements and shutters.

The following references relate generally to thin film technology,semiconductor processing, optical monitoring, and crystal monitoring:(1) “Optical Monitoring of Thin-Film Thickness,” R. Richier, A. Fornier,and E. Pelletier, Ch. 3, pages 57-90, Thin Films for Optical Systems(Optical Engineering), Edited by Francois R. Flory and M. Mekker, ISBN0824796330, Marcel Dekker Jul. 1, 1995; (2) “Deposition Technologies andApplications: Introduction and Overview,” Werner Kern and KlausSchuegraf, pages 1-25, HandBook of Thin-film Deposition Processes andTechniques, Principles, Methods, Equipment, and Applications, Edited byKlaus K. Schuegraf, Noyes Publications, ISBN 0-8155-1153-1, 1988. (3)“Introduction to Sputtering,” Brian Chapman and Stefano Mangano, pages291-318, HandBook of Thin-film Deposition Processes and Techniques,Principles, Methods, Equipment, and Applications, Edited by Klaus K.Schuegraf, Noyes Publications, ISBN 0-8155-1153-1, 1988; and (4) C. U.Lu and O. Lewis, J. Appl. Phys. 43, p 4385 (1972).

STATEMENTS REGARDING INCORPORATION BY REFERENCE AND VARIATIONS

All references cited throughout this application, for example patentdocuments including issued or granted patents or equivalents; patentapplication publications; and non-patent literature documents or othersource material are hereby incorporated by reference herein in theirentireties, as though individually incorporated by reference, to theextent each reference is at least partially not inconsistent with thedisclosure in this application (for example, a reference that ispartially inconsistent is incorporated by reference except for thepartially inconsistent portion of the reference).

Every formulation or combination of components described or exemplifiedherein can be used to practice the invention, unless otherwise stated.

Whenever a range is given in the specification, for example, atemperature range, a time range, or a composition or concentrationrange, all intermediate ranges and subranges, as well as all individualvalues included in the ranges given are intended to be included in thedisclosure. It will be understood that any subranges or individualvalues in a range or subrange that are included in the descriptionherein can be excluded from the claims herein.

All patents and publications mentioned in the specification areindicative of the levels of skill of those skilled in the art to whichthe invention pertains. References cited herein are incorporated byreference herein in their entirety to indicate the state of the art asof their publication or filing date and it is intended that thisinformation can be employed herein, if needed, to exclude specificembodiments that are in the prior art.

As used herein, “comprising” is synonymous with “including,”“containing,” or “characterized by,” and is inclusive or open-ended anddoes not exclude additional, unrecited elements or method steps. As usedherein, “consisting of” excludes any element, step, or ingredient notspecified in the claim element. As used herein, “consisting essentiallyof” does not exclude materials or steps that do not materially affectthe basic and novel characteristics of the claim. In each instanceherein any of the terms “comprising”, “consisting essentially of” and“consisting of” may be replaced with either of the other two terms. Theinvention illustratively described herein suitably may be practiced inthe absence of any element or elements, limitation or limitations whichis not specifically disclosed herein.

One of ordinary skill in the art will appreciate that startingmaterials, materials, reagents, synthetic methods, purification methods,analytical methods, assay methods, and methods other than thosespecifically exemplified can be employed in the practice of theinvention without resort to undue experimentation. All art-knownfunctional equivalents, of any such materials and methods are intendedto be included in this invention. The terms and expressions which havebeen employed are used as terms of description and not of limitation,and there is no intention that in the use of such terms and expressionsof excluding any equivalents of the features shown and described orportions thereof, but it is recognized that various modifications arepossible within the scope of the invention claimed. Thus, it should beunderstood that although the present invention has been specificallydisclosed by preferred embodiments and optional features, modificationand variation of the concepts herein disclosed may be resorted to bythose skilled in the art, and that such modifications and variations areconsidered to be within the scope of this invention as defined by theappended claims.

EXAMPLE 1 Film Thickness Monitoring and Control Methods Using an OpticalSensor

The present invention includes methods and devices having a movingoptical sensor that is capable of movement along a trajectory in a fluxregion of a thin film processing system that is substantially coincidentwith the trajectories of one or more substrates undergoing translationand/or rotating during thin film processing. FIG. 9A shows a schematicdiagram illustrating a moveable optical sensor of the present inventionfor positioning on a means for translating the sensor in the flux regionof a thin film processing system. Moveable optical sensor 700 comprisesoptical source 705, sensor substrate 710, detector 715, and wirelesstransmitter 716. Each of these elements are provided in housing element717, which is capable of integration with a means of translation, suchas integration with a sub-planet of a dual rotation planetary system.

Optical source 705 generates optical beam 706 that is directed onto afixed position sensor substrate 710 supported by mounting elements 714.Fixed position sensor substrate 710 is positioned such that externalsurface 720 is exposed to a flux of precursors in a thin film processingsystem, and internal surface 721 is positioned such that it is exposedto optical beam 706. In the exemplary embodiment shown in FIG. 9A, thinfilm processing system is a vapor deposition system and external surface720 is exposed to precursors, thereby resulting in formation of one ormore thin films 725 on external surface 720. Optical beam 706 interactswith sensor substrate 710 and thin film(s) 725, thereby generatingreflected beams 707 at external surface 720, interfaces between thinfilm layers and the interface between the thin film layer(s) and theprocessing chamber, which are detected by detector 715. Detector 715 maybe configured to detect the intensity of the reflected beams 707, thepolarization states of the reflected beams 707, the frequencydistributions of the reflected beams 707 or any combination of these asa function of time. The output from detector 715 is provided to wirelesstransmitter which generates a wireless output signal that is sent toreceiver 735. In one embodiment, sensor substrate comprises the samematerial(s) and has the same shape as a substrate(s) undergoing thinfilm processing.

In an embodiment useful for monitoring the optical thickness of thinfilm(s) 725 on external surface 720, light source 705 generates acoherent optical beam 706. In this embodiment, the beams reflected atexternal surface 720, interfaces between thin film layers and theinterface between the thin film layer(s) and the processing chamberundergo constructive and/or destructive optical interference, andmeasurement of the intensity of detected light as a function of timeprovides a means of determining the optical thickness of thin film(s)725 on external surface 720. In another embodiment, the frequency of thedetected light is systematically varied to provide a measurement of theabsorption and/or transmission spectrum of thin film(s) 725 on externalsurface 720. In other useful embodiments, optical source optical source705 and detector 715 are configured such that the refractive index,morphology and/or composition of thin film(s) 725 on external surface720 is monitored in real time.

Optical sources 705 useable in this aspect of the present inventioninclude tunable narrow band optical sources such as tunable diodelasers, fixed frequency narrow band optical sources such as a HeNelaser, narrow band optical sources providing a plurality of narrow bandsof light, broad band sources such as blackbody sources or light emittingdiodes or any combination of these. Optical sources and detectors may beprovided with additional optical components(not shown in FIG. 9A) forfiltering the frequencies of optical beam incident on internal surface721 and/or the detected light, such as Fabry-Perot etalons filters(tunable or fixed frequency), spectrometers, gratings and prisms.Optionally, detector 715 is operably connected to a microprocessor (notshown in FIG. 9A) that processes output signals generated by detector715, thereby generating real time measurements of optical thickness,physical thickness, refractive index, composition,absorption/transmission spectrum and/or morphology of the thin film(s)725 on external surface 720. In this embodiment, real time measurementsare provided to wireless transmitter 716 which generates output signalstransmitted to receiver 735 corresponding to the real time measurements.Detectors 715 useful for the present methods and devices includephotodiodes, diode arrays, photomultiplier tubes, detector arrays,charge coupled devices and all equivalents.

FIG. 9B is a schematic diagram illustrating a moveable optical sensorcapable of spatially characterizing thin film(s) deposited on theexternal surface of a sensing substrate. As shown in FIG. 9B, themoveable optical sensor 800 further comprises a means 810 fortranslating optical beam 706 across external surface 720 of sensorsubstrate 710. In the. embodiment illustrated in FIG. 9B, means 810 fortranslating optical beam 706 across external surface 720 comprises apartially reflective reflector 810 provided in optical communicationwith optical source 705 and capable of rotation about one or morerotational axes (schematically indicated by arrows 820). Rotation of thepartially reflective reflector 810 directs optical beam 706 to differentregions on thin film(s) 725, thereby providing a means of accuratelyspatially characterizing the optical thicknesses, physical thicknesses,compositions, morphology, absorption/transmission spectra, refractiveindices or any combination of these of thin film(s) 725. As shown inFIG. 9A, partially reflective reflector 810 is also capable oftransmitting at least a portion of light reflected by sensor substrate710 and thin film(s) 725 such that it can be detected by detector 715.

Use of a moveable optical sensor provides several advantages beneficialfor certain applications of the devices and methods of the presentinvention. First, movable optical sensors are capable of providingaccurate real time measurements of the optical thicknesses of thinfilm(s) processed on substrates. Importantly, these measurements do notrely on assumed densities, compositions, and/or refractive indices ofprocessed materials. Furthermore, optical sensors provide opticalthickness measurements with enhanced accuracy for certain fabricationapplications, such as fabrication of narrow band optical filters.Second, movable optical sensors are capable of measuring the refractiveindex, transmission spectrum and/or absorption spectrum of processedmaterial on the sensor substrate in real time. Finally, use of opticalsensors having a means for translating the optical beam incident to thesensor substrate provides an effective means for spatiallycharacterizing physical, optical and chemical properties of depositedthin films.

EXAMPLE 2 Film Thickness Monitoring and Control Methods Incorporating anSC Cut Quartz Crystal Monitor

Thin film processing systems and related methods of the presentinvention having a deposition sensor that moves along a trajectory thatis substantially coincident with the trajectories of substratesundergoing processing enables realization of significant furtherimprovements in film thickness control. In one embodiment, thin filmprocessing systems of the present invention further comprise a moveablequartz crystal microbalance deposition sensor having a doubly rotatedcut, such as an SC-cut, capable of operation in a manner that issignificantly less susceptible to film thickness errors arising fromchanges in the temperature of the sensor and stress exerted on thesensor by deposited films than conventional AT cut quartz crystaldeposition sensors. Use of a moveable SC-cut quartz crystal microbalancedeposition sensor capable of movement along a trajectory substantiallycoincident with the trajectories of substrates undergoing processing andcapable of excitation on at least two different modes, for example,leads to unprecedented gains in thickness control, thereby providing arobust fabrication platform for producing a range thin film structuresand devices having film thicknesses selected with enhanced accuracy andexhibiting enhanced piece-to-piece uniformity.

In fixed-sensor monitoring and control systems the errors caused by achanging parts-to-monitor ratio are typically large enough to overwhelmother sources of error in the sensor measurement, such as errors arisingfrom changes in the temperature and the stress environment of a quartzcrystal deposition sensor, rendering these other sources of errorirrelevant with respect to the degree of processing control provided bythe system. Elimination of errors due to the fluctuations of theparts-to-monitor ratio in thin-film coating achieved by using a sensorthat follows a path that is substantially coincident with the path ofthe parts (i.e. substrates) undergoing processing allows for furtherimprovement in layer thickness control by minimizing or eliminatingother sources of error in the quartz crystal microbalance depositionsensor. Two significant sources of error common to measurements made byquartz-crystal microbalance deposition sensors are temperaturefluctuations and coating-applied stress. In this example, systems andmethods are provided that minimize or eliminate processing thicknesscontrol errors arising from these sources.

Thin films produced by ion beam sputtering deposition and otherdeposition techniques have a large amount of stress. Stresses in adeposited single or multi-layer film on a quartz crystal microbalancedeposition sensor may give rise to significant sources of error oruncertainty in layer thickness control. Quartz crystal microbalancescomprise quartz crystals cut from a bulk crystal with the crystal axesin different orientations relative to the normal of the sensing surface(or coating surface) of the microbalance. The various crystal cuts havedifferent physical, mechanical and electrical properties, and inparticular they have different sensitivities to temperature and surfacestress. The industry standard for optical thin-film monitors is theAT-cut of quartz, which provides a fundamental mode of oscillation witha frequency that can be relatively insensitive to temperaturefluctuations over a narrow range of temperatures. The frequencies ofAT-cut crystals, however, tend to be somewhat sensitive to accumulatedstresses in the deposited film. Moreover, the stress coefficient (i.e.the amount of frequency change per unit of stress) exhibits substantialvariation from crystal to crystal. Even if more accurate cutting of thequartz crystals could lead to a more consistent stress coefficient, thestress levels in a single or multi-layer thin film structure are unknownand difficult to predict for a particular thin film design. The effectof this uncertain or uncharacterized stress and the random nature of thestress coefficient of these quartz crystal microbalances lead tosignificant errors in layer thickness.

Doubly rotated quartz crystal cuts, such as a SC-cut, have anoscillation mode with a frequency that is much less sensitive to stressin the deposited film. A second advantage of a SC-cut crystal (andcertain other cuts) is that the temperature of the crystal can bemonitored by measuring and comparing frequencies of two differentoscillation modes of the crystal, because different modes have differenttemperature coefficients (i.e. change in frequency per unit change intemperature). Use of a quartz microbalance deposition sensor having aSC-cut quartz crystal that moves on a path that is substantiallycoincident with the parts that are being coated, provides a layerthickness control system that is more accurate than a deposition sensorbased on an AT-cut crystal that also moves on a substantially coincidentpath.

Thin film deposition processes put a significant thermal load on thecrystal of a quartz crystal microbalance deposition sensor and on thesurrounding body of the crystal holder. When the deposition beam isturned on, the crystal is heated on a timescale associated with thethermal properties of the crystal itself. The warming of the crystalholder and surrounding structure occurs on a second timescale that isusually longer. Because much of the thermal load is directly on thecrystal, it is difficult to infer the temperature of the crystal fromseparate temperature sensors which cannot be mounted directly on thecrystal. By monitoring frequencies of two oscillation modes of thequartz crystal, however, we can infer the temperature of the crystal.Experiments show that the dependence of the frequencies of the two modes(labeled here with subscripts A and B) on temperature and mass can bewell approximated by f_(A)(m, T)=g_(A)(m)+h_(A)(T) and f_(B)(m,T)=g_(B)(m)+h_(B)(T), where f_(i)(m, T)=[F_(i0)−F_(i)(m, T)]/F_(i0) arefractional frequency changes from the initial (unloaded) frequencyF_(i0) for each mode, i=A,B. Here h_(i)(T) are functions that can bemeasured by warming the crystal without deposition, and g_(i)(m) arefunctions of mass that do not tend to change much from crystal tocrystal, and can be measured by loading a crystal by varying amounts ofdeposited film and then measuring the frequencies at a fixed temperaturewithout the deposition beam on. Given these known functions,measurements of the initial frequencies for the two modes, andmeasurements of the frequencies of the two modes, we can solve these twoequations for unknown values of T and m (now corrected for temperature).This can be carried out during the deposition process while thermalloading is occurring.

FIG. 10 shows a block diagram of an electronic circuit for monitoringthe resonant frequencies of two (or several) modes of a quartzmicrobalance crystal. The measurement of the frequencies of the twomodes is performed using a circuit based on an on-board computer, acomputer-controlled frequency synthesizer, an RF power amplifier, an RFpower detector, and an analog-to-digital converter. The arrows show theflow of information. In one embodiment, the measurement is a two-stepprocess. First, in order to locate the mode frequencies of the crystalapproximately, the frequency of the frequency synthesizer,(f ) is sweptthough a range of frequencies containing one of the mode resonancefrequencies. The AC current on the crystal rises and passes through amaximum when the frequency of the synthesizer approaches and passesthrough the resonance frequency of the first mode (mode A). Thisamplitude is converted to a DC voltage by the RF power detector, whichwe call the DC resonance amplitude signal, V_(A)(f). This signal is thenconverted to a digital number which is repeatedly read by the computeras the frequency sweep proceeds. The center frequency will be near thelocation of the maximum. Another range of frequencies that contains theresonance frequency of the next mode (mode B) is swept and the maximumof the corresponding resonance amplitude signal, V_(B)(f) locatesapproximately that resonance frequency. After the mode frequencies arelocated approximately using this procedure, a locking scheme based onsquare wave frequency modulation is used to measure and follow theresonant frequency more precisely. For a frequency f near resonance A,the frequency of the synthesizer is stepped alternately to frequenciesshifted slightly on either side of the resonance by a frequencymodulation amplitude, Δf, f±Δf. The modulation amplitude Δf is on theorder of the half width of the peaked curve measured in the first stepof the measurement. At each of these frequencies the resonance amplitudesignals are read, and the central frequency f is adjusted in proportionto the difference: V_(A)(f−Δf)−V_(A)(f+Δf) so as to force thisdifference to zero. When this is true, the central frequency is therefined measurement of the resonance frequency of mode A: f_(A)=f . Thenthe system repeats this to measure the resonance frequency of the secondmode (mode B), thus finding the refined resonance frequency f_(B). Fromthese two measurements, the temperature and thickness (corrected fortemperature) are found as described above.

As will be obvious to one of skill in the art, other readout circuitsand electronic systems can be used in the present invention formeasuring the frequency of A and B modes (an optionally other modes) ofthe SC cut quartz microbalance deposition sensor. In addition to readoutcircuits that excite A and B modes sequentially, the present inventionincludes readout circuits capable of simultaneously exciting A and Bmodes such as those described in U.S. Pat. Nos. 5,869,763, 4,872,765 and4,079,280.

The mode frequencies can also be determined by using the crystal in anactive oscillator with a switchable filter to alternately isolate thetwo modes of oscillation, and a frequency counter. Fundamental modeSC-cut quartz crystal microbalances exhibit resonances in two distinctmodes. These modes are called the c-mode and the b-mode. In oneembodiment, f_(A) corresponds to the resonance frequency of the c-mode,and f_(B) corresponds to the resonance frequency of the b-mode. For anovertone SC-cut quartz crystal microbalance there are four distinctmodes of oscillation: fundamental c-mode, fundamental b-mode, overtonec-mode, overtone b-mode. For the overtone SC-cut quartz crystalmicrobalance there are three embodiments: (1) f_(A) corresponds toovertone c-mode and f_(B) corresponds to fundamental b-mode; (2) f_(A)corresponds to overtone c-mode and f_(B) corresponds to overtone b-mode;(3) f_(A) corresponds to overtone c-mode and f_(B) corresponds tofundamental c-mode.

The time sequence of thickness measurements obtained in this way is thenused to control the deposition process as described herein. FIGS. 11Aand 11B shows the process improvements of the monitor based on theSC-cut quartz crystal with temperature corrections as described in theprevious paragraph, compared to the monitor based on the AT-cut quartzcrystal. FIG. 11A corresponds to deposition control provided by anAT-cut quartz crystal microbalance and FIG. 11B corresponds todeposition control provided by an SC-cut quartz crystal microbalance. Inboth cases, the monitor follows a substantially coincident trajectorywith the parts, in order to eliminate or reduce errors caused byfluctuations in the parts-to-monitor ratio. The multi-layer thin filmcoating is designed to make a sharp-edge filter. In both cases themonitors are traveling on paths that are substantially coincident withthe parts (e.g. substrates), and the optical spectra of the resultingparts are shown for five nearly successive runs. Note that the centering(horizontal location of the edge) is better controlled for the SC-cutquartz crystal microbalance, and the shape of the high-transmitting edgeis more consistent as well. Both the better centering and the moreconsistent shape are reflections of improved layer thickness control.

Use of a moving deposition sensor (e.g. SC-cut or AT-cut quartz crystalmicrobalance) that moves along a trajectory that is substantiallycoincident with the trajectories of substrates undergoing processingenables the physical thickness of deposited thin films to be selected towithin 1.2%. Use of the combination of a moving deposition sensor movesalong a trajectory that is substantially coincident with thetrajectories of substrates undergoing processing having a SC-cut quartzcrystal microbalance that is excited on two or more modes, however,enables the physical thickness of deposited thin films to be selected towithin 0.3%. This enhancement in thickness control constitutes animprovement over conventional methods using a fixed position AT-Cutquartz crystal microbalance equal to about a factor of ten.

1. A device for processing a thin film on a substrate, said devicecomprising: a thin film deposition source for generating a flux ofprecursors in a flux region; a means for rotating said substrate,wherein said substrate has a receiving surface for receiving saidprecursors, wherein rotation of said substrate rotates said receivingsurface about a first rotational axis; a means for translating saidrotating substrate in said flux region; a sensor having a sensingsurface for receiving said precursors; a means for rotating said sensor,wherein rotation of said sensor rotates said sensing surface about asecond rotational axis; and a means for translating said rotating sensorin said flux region; wherein rotation and translation of said substratemoves said receiving surface along a receiving surface trajectory insaid flux region and wherein rotation and translation of said sensormoves said sensing surface along a trajectory in said flux region thatis substantially coincident with said receiving surface trajectory. 2.The device of claim 1 wherein rotation and translation of said substrateand said sensor results in substantially the same average fluxes ofprecursors to said receiving surface and said sensing surface for aselected deposition time.
 3. The device of claim 1 wherein the receivingsurface of the substrate and the sensing surface of the sensorsimultaneously receive said precursors.
 4. The device of claim 1 whereinsaid means for translating said rotating substrate and said means fortranslating said rotating sensor comprise a central planet of a dualrotation planetary system, wherein rotation of said central planet movessaid rotating substrate and said rotating sensor in an orbit about acentral rotational axis of said dual rotation planetary system andwherein said first and second rotational axes are positioned the samedistance from said central rotational axis.
 5. The device of claim 4wherein rotation of said central planet moves said rotating substrateand said rotating sensor in a circular orbit about said centralrotational axis of said dual rotation planetary system.
 6. The device ofclaim 4 wherein said means for rotating said substrate is a substratesub-planet of said dual rotation planetary system, wherein rotation ofsaid substrate sub-planet rotates said receiving surface about saidfirst rotational axis.
 7. The device of claim 4 wherein said means forrotating said sensor is a sensor sub-planet of said dual rotationplanetary system, wherein rotation of said sensor sub-planet rotatessaid sensing surface about said second rotational axis.
 8. The device ofclaim 1 wherein said sensor further comprises a wireless transmitter forgenerating an output signal corresponding to a measurement made by saidsensor, wherein said output signal comprises infrared radiation, radiowaves or both.
 9. The device of claim 8 further comprising a receiverfor receiving said output signal generated from said transmitter. 10.The device of claim 9 further comprising a thin film deposition sourcecontroller in communication with said receiver for receiving said outputsignal, wherein said thin film deposition source controller controls thesource distribution profile of precursors in said flux region.
 11. Thedevice of claim 1 wherein said sensor is a mass sensor for measuring themass of precursors deposited on said sensing surface.
 12. The device ofclaim 11 wherein said mass sensor is a quartz crystal microbalancedeposition sensor having an SC-cut quartz crystal that is capable ofexcitation of at least two different modes, wherein said modes areselected from the group consisting of: a fundamental c-mode, afundamental b-mode, an overtone c-mode, and an overtone b-mode.
 13. Thedevice of claim 11 wherein the mass sensor further comprise circuitryfor reading said sensor, and wherein said circuitry is positioned suchthat it rotates and translates with said sensing surface.
 14. The deviceof claim 1 wherein said sensor is selected from the group consisting of:an optical thickness monitor for measuring the optical thickness of athin film of precursors on said sensing surface; a temperature sensorfor measuring the temperature of said sensing surface; a refractiveindex monitor for measuring the refractive index of a thin film ofprecursors on said sensing surface; an electrometer for measuring theelectric charge of a thin film of precursors on said sensing surface;and an accelerometer for measuring the acceleration of said rotatingsensor.
 15. The device of claim 1 where said sensor comprises aplurality of different sensors selected from the group consisting of: amass sensor; an optical thickness monitor; a temperature sensor; arefractive index monitor; an electrometer; and an accelerometer.
 16. Thedevice of claim 1 wherein said sensor comprises a sensor array, whereinsaid sensor array comprises a plurality of sensors positioned atdifferent distances from said second rotational axis.
 17. The device ofclaim 1 wherein said sensor is powered by a wireless means of providingpower, wherein said wireless means of providing power is capable ofproviding power to said sensor radiatively, magnetically, mechanicallyor using an on-board battery power source.
 18. A device for processing athin film on a substrate, said device comprising: a thin film depositionsource for generating a flux of precursors in a flux region; a means fortranslating said substrate, wherein said substrate has a receivingsurface for receiving said precursors; wherein translation of saidsubstrate moves said receiving surface along a receiving surfacetrajectory in said flux region; a quartz crystal microbalance depositionsensor comprising a quartz crystal having an SC cut and having a sensingsurface for receiving said precursors; a means for translating saidquartz crystal microbalance deposition sensor, wherein translation ofsaid quartz crystal microbalance deposition sensor moves said sensingsurface along a sensor trajectory in said flux region that issubstantially coincident with said receiving surface trajectory.
 19. Thedevice of claim 18 wherein said means for translating said substrate andsaid means for translating said sensor comprise a dual rotationplanetary system.
 20. The device of claim 18 further comprising areadout circuit electrically connected to said quartz crystalmicrobalance deposition sensor, wherein said readout circuit is capableof exciting at least two different modes of said quartz crystal havingsaid SC cut, wherein said modes are selected from the group consistingof: a fundamental c-mode, a fundamental b-mode, an overtone c-mode, andan overtone b-mode.
 21. A method for monitoring processing of a thinfilm on a substrate, said method comprising the steps of: providing athin film deposition source for generating a flux of precursors in aflux region, providing a substrate having a receiving surface forreceiving said precursors; providing a quartz crystal microbalancedeposition sensor comprising a quartz crystal having an SC cut andhaving a sensing surface for receiving said precursors; translating saidsubstrate in said flux region, wherein translation of said substratemoves said receiving surface along a receiving surface trajectory insaid flux region; translating said quartz crystal microbalancedeposition sensor in said flux region, wherein translation of saidquartz crystal microbalance deposition sensor moves said sensing surfacealong a trajectory in said flux region that is substantially coincidentto said receiving surface trajectory; and making a measurement of aphysical, optical or chemical property of a thin film on said sensingsurface of said sensor, thereby monitoring processing of said thin filmon said substrate.
 22. The method of claim 21 wherein said quartzcrystal microbalance deposition sensor further comprises a wirelesstransmitter, said method further comprising the step of transmitting anoutput signal corresponding to said measurement from said wirelesstransmitter to a receiver.
 23. The method of claim 21 further comprisingthe step of exciting at least two modes of said quartz crystal having anSC cut, wherein said modes are selected from the group consisting of: afundamental c-mode, a fundamental b-mode, an overtone c-mode, and anovertone b-mode.
 24. A method for controlling the thickness of a thinfilm deposited on a substrate, said method comprising the steps of:providing a thin film deposition source for generating a flux ofprecursors in a flux region, providing a substrate having a receivingsurface for receiving said precursors; providing a quartz crystalmicrobalance deposition sensor comprising a quartz crystal having an SCcut and having a sensing surface for receiving said precursors;translating said substrate in said flux region, wherein translation ofsaid substrate moves said receiving surface along a receiving surfacetrajectory in said flux region; translating said quartz crystalmicrobalance deposition sensor in said flux region, wherein translationof said quartz crystal microbalance deposition sensor moves said sensingsurface along a trajectory in said flux region that is substantiallycoincident to said receiving surface trajectory; determining an observedthicknesses of a thin film deposited on said sensing surface; andcomparing said observed thickness to a preselected thickness; andstopping said flux of precursors to said receiving surface when saidobserved thickness is equal to or greater than said preselectedthickness.